Probleme beim aufrufen von Funktionen Powershell GUI

# Install .Net Assemblies
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
[Windows.Forms.Application]::EnableVisualStyles()

################################################################## Variables 
###Main Window###
$mainForm         = New-Object System.Windows.Forms.Form

###Menu bar###
$menuMain         = New-Object System.Windows.Forms.MenuStrip

###Menu###
$menuFile         = New-Object System.Windows.Forms.ToolStripMenuItem
$menuPrograms     = New-Object System.Windows.Forms.ToolStripMenuItem

###Items of $menuFile###
$menuPSTool1      = New-Object System.Windows.Forms.ToolStripMenuItem
$menuPSTool2      = New-Object System.Windows.Forms.ToolStripMenuItem
$menuExit         = New-Object System.Windows.Forms.ToolStripMenuItem

###Items of $menuPrograms###
$menuPSTool3      = New-Object System.Windows.Forms.ToolStripMenuItem

###Tool1###
$tool1TextBox      = New-Object System.Windows.Forms.TextBox
$tool1Label        = New-Object System.Windows.Forms.Label
$tool1Button       = New-Object System.Windows.Forms.Button

###Tool2###
$tool2TextBox      = New-Object System.Windows.Forms.TextBox
$tool2Label        = New-Object System.Windows.Forms.Label
$tool2Button       = New-Object System.Windows.Forms.Button

###Status###
$statusStrip      = New-Object System.Windows.Forms.StatusStrip
$statusLabel      = New-Object System.Windows.Forms.ToolStripStatusLabel

################################################################## Icons
$code = @"  
using System;
using System.Drawing;
using System.Runtime.InteropServices;

namespace System
{
	public class IconExtractor
	{

	 public static Icon Extract(string file, int number, bool largeIcon)
	 {
	  IntPtr large;
	  IntPtr small;
	  ExtractIconEx(file, number, out large, out small, 1);
	  try
	  {
	   return Icon.FromHandle(largeIcon ? large : small);
	  }
	  catch
	  {
	   return null;
	  }

	 }
	 [DllImport("Shell32.dll", EntryPoint = "ExtractIconExW", CharSet = CharSet.Unicode, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]  
	 private static extern int ExtractIconEx(string sFile, int iIndex, out IntPtr piLargeVersion, out IntPtr piSmallVersion, int amountIcons);

	}
}
"@  
Add-Type -TypeDefinition $code -ReferencedAssemblies System.Drawing

# Extract PowerShell Icon from PowerShell Exe
$iconPS   = [Drawing.Icon]::ExtractAssociatedIcon((Get-Command powershell).Path)

# Set font style and size for entire gui
$font = New-Object System.Drawing.Font("Arial",12,[System.Drawing.FontStyle]::Regular)  

################################################################## Main Form Setup
$mainForm.Icon            = $iconPS
$mainForm.MainMenuStrip   = $menuMain
$mainForm.Height          = 600
$mainForm.Width           = 800
$mainForm.StartPosition   = "CenterScreen"  
$mainForm.TopMost         = $true
$mainForm.Text            = "Maske PowerBox"  
$mainForm.Font            = $font
$mainForm.Controls.Add($menuMain)

################################################################## Menu

# Main Menu Bar
[void]$mainForm.Controls.Add($menuMain)

# Menu Options - File
$menuFile.Text = "&File"  
[void]$menuMain.Items.Add($menuFile)

# Menu Options - Programs
$menuPrograms.Text = "&Programs"  
[void]$menuMain.Items.Add($menuPrograms)

# Menu Options - File / get-LoggedInUserRemotePC
$menuPSTool1.Image = [System.IconExtractor]::Extract("shell32.dll", 170, $true)  
$menuPSTool1.ShortcutKeys = "Control, Q"  
$menuPSTool1.Text = "Get-User"  
$menuPSTool1.Add_Click({get-LoggedInUserRemotePC})
[void]$menuFile.DropDownItems.Add($menuPSTool1)

# Menu Options - File / get-LoggedInUserRemotePC
$menuPSTool2.Image = [System.IconExtractor]::Extract("shell32.dll", 76, $true)  
$menuPSTool2.ShortcutKeys = "Control, W"  
$menuPSTool2.Text = "Get-FreeSpace"  
$menuPSTool2.Add_Click({get-FreeSpaceOfRemotePC})
[void]$menuFile.DropDownItems.Add($menuPSTool2)

# Menu Options - File / update-GlobalAddressBook
$menuPSTool3.Image = [System.IconExtractor]::Extract("shell32.dll", 13, $true)  
$menuPSTool3.ShortcutKeys = "Control, E"  
$menuPSTool3.Text = "Update-GlobalAddressBook"  
$menuPSTool3.Add_Click({update-GlobalAddressBook})
[void]$menuPrograms.DropDownItems.Add($menuPSTool3)

# Menu Options - File / Exit
$menuExit.Image = [System.IconExtractor]::Extract("shell32.dll", 10, $true)  
$menuExit.ShortcutKeys = "Control, X"  
$menuExit.Text = "&Exit"  
$menuExit.Add_Click({$mainForm.Close()})
[void]$menuFile.DropDownItems.Add($menuExit)

################################################################## Status Bar
[void]$statusStrip.Items.Add($statusLabel)
$statusLabel.AutoSize  = $true
$statusLabel.Text      = "Ready..."  
$mainForm.Controls.Add($statusStrip)

################################################################## functions
function get-LoggedInUserRemotePC {

    $statusLabel.Text = "Wait for input..."  

    $tool1Label.Text = "Computername eingeben:"  
    $tool1Label.Location = New-Object System.Drawing.Size(40,44)
    $tool1Label.Size = New-Object System.Drawing.Size(200,20)
    [void]$mainForm.Controls.Add($tool1Label)

    $tool1TextBox.Text = "ADMCB"  
    $tool1TextBox.Location = New-Object System.Drawing.Size(40,80)
    $tool1TextBox.Size = New-Object System.Drawing.Size(200,20)
    $tool1TextBox.Multiline = $true
    [void]$mainForm.Controls.Add($tool1TextBox)

    $tool1Button.Text = "Get-User"  
    $tool1Button.Location = New-Object System.Drawing.Size(240,40)
    $tool1Button.Autosize = $true
    $tool1Button.Add_Click({

        $computerName = $tool1TextBox.Text    
    
        $users = Get-WmiObject -Class win32_process -ComputerName $computerName | Where-Object{ $_.Name -eq "explorer.exe" } | ForEach-Object{ ($_.GetOwner()).Domain + "\" + ($_.GetOwner()).User; }  
        
        Write-Host $users

    })
    [void]$mainForm.Controls.Add($tool1Button)
}# get-LoggedInUserRemotePC

function get-FreeSpaceOfRemotePC {

    $statusLabel.Text = "Wait for input..."  

    $tool2Label.Text = "Computername eingeben:"  
    $tool2Label.Location = New-Object System.Drawing.Size(40,44)
    $tool2Label.Size = New-Object System.Drawing.Size(200,20)
    [void]$mainForm.Controls.Add($tool2Label)

    $tool2TextBox.Text = "ADMCB"  
    $tool2TextBox.Location = New-Object System.Drawing.Size(40,80)
    $tool2TextBox.Size = New-Object System.Drawing.Size(200,20)
    $tool2TextBox.Multiline = $true
    [void]$mainForm.Controls.Add($tool2TextBox)

    $tool2Button.Text = "Get-User"  
    $tool2Button.Location = New-Object System.Drawing.Size(240,40)
    $tool2Button.Autosize = $true
    $tool2Button.Add_Click({

        $computerName = $tool2TextBox.Text    
    
        $freeSpace = gwmi Win32_LogicalDisk -ComputerName $computerName | ForEach {$_.name, ($_.freespace / 1GB)}
        
        Write-Host $freeSpace

        $statusLabel.Text = "Ready..."  
    })
    [void]$mainForm.Controls.Add($tool2Button) 
}# get-FreeSpaceOfRemotePC

function update-GlobalAddressBook {

    #Globles Adressbuch aktualisieren um Änderungen direkt anzuzeigen
    $statusLabel.Text = "Updating Global Adressbook...";Start-Sleep 1  
    get-addresslist | update-addresslist
    $statusLabel.Text = "Updating...please wait 3...";Start-Sleep 1  
    get-globaladdresslist | update-globaladdresslist
    $statusLabel.Text = "Updating...please wait 2...";Start-Sleep 1  
    get-offlineaddressbook | update-offlineaddressbook
    $statusLabel.Text = "Updating...please wait 1...";Start-Sleep 1  
    $statusLabel.Text = "Ready..."  
}

# Show Main Form
[void] $mainForm.ShowDialog()