Checkbox bei Office-Ribbons

Function checkboxGetPressed(control As Office.IRibbonControl) As Boolean
    'Return True to get the Checkbox to be in pressed state, and false for unchecked   
End Function

<?xml version="1.0" encoding="UTF-8"?> 
<customUI onLoad="Ribbon_Load" xmlns="http://schemas.microsoft.com/office/2006/01/customui"> 
    <ribbon>
        <tabs>
            <tab id="myTab" label="MyTab"> 
                <group id="myGroup" label="Meine Gruppe"> 
                    <checkBox id="CheckBox1" label="CheckBox1" getPressed="checkboxGetPressed" /> 
                </group>
            </tab>
        </tabs>
    </ribbon>
</customUI>

<?xml version="1.0" encoding="UTF-8"?> 
<customUI onLoad="Ribbon_Load" xmlns="http://schemas.microsoft.com/office/2006/01/customui"> 
    <ribbon>
        <tabs>
            <tab id="myTab" label="MyTab" > 
                <group id="myGroup" label="Meine Gruppe"> 
                    <checkBox id="CheckBox1" label="CheckBox1" getPressed="checkboxGetPressed" /> 
                </group>
            </tab>
        </tabs>
    </ribbon>
</customUI>

<Runtime.InteropServices.ComVisible(True)> _
    Public Class Ribbon
    Implements Office.IRibbonExtensibility

    Public ribbon As Office.IRibbonUI

    Public Sub New()
    End Sub

    Public Function GetCustomUI(ByVal ribbonID As String) As String Implements Office.IRibbonExtensibility.GetCustomUI
        Return GetResourceText("WorkbookTriggerCheckbox.Ribbon.xml")  
    End Function

#Region "Ribbon Callbacks" 
    'Create callback methods here. For more information about adding callback methods, select the Ribbon XML item in Solution Explorer and then press F1.  
    Public Sub Ribbon_Load(ByVal ribbonUI As Office.IRibbonUI)
        Me.ribbon = ribbonUI
        Globals.ThisWorkbook.rib = ribbonUI
    End Sub

    Function checkboxGetPressed(control As Office.IRibbonControl) As Boolean
        If Globals.ThisWorkbook.enableCheckbox Then
            Return True
        Else
            Return False
        End If
    End Function
#End Region

#Region "Helpers" 

    Private Shared Function GetResourceText(ByVal resourceName As String) As String
        Dim asm As Reflection.Assembly = Reflection.Assembly.GetExecutingAssembly()
        Dim resourceNames() As String = asm.GetManifestResourceNames()
        For i As Integer = 0 To resourceNames.Length - 1
            If String.Compare(resourceName, resourceNames(i), StringComparison.OrdinalIgnoreCase) = 0 Then
                Using resourceReader As IO.StreamReader = New IO.StreamReader(asm.GetManifestResourceStream(resourceNames(i)))
                    If resourceReader IsNot Nothing Then
                        Return resourceReader.ReadToEnd()
                    End If
                End Using
            End If
        Next
        Return Nothing
    End Function

#End Region

End Class

Public Class ThisWorkbook
    Public enableCheckbox As Boolean = False
    Public rib As Office.IRibbonUI

    Private Sub ThisWorkbook_SheetChange(Sh As Object, Target As Microsoft.Office.Interop.Excel.Range) Handles Me.SheetChange
        If Sh.Name = "Tabelle1" And Not ThisApplication.Intersect(Sh.Range("A1"), Target) Is Nothing Then  
            If Target.Value = 1 Then
                enableCheckbox = True
            Else
                enableCheckbox = False
            End If
            rib.InvalidateControl("CheckBox1")  
        End If
    End Sub

    Private Sub ThisWorkbook_Shutdown() Handles Me.Shutdown
    End Sub

    Protected Overrides Function CreateRibbonExtensibilityObject() As Microsoft.Office.Core.IRibbonExtensibility
        Return New Ribbon()
    End Function
End Class