Excel Datenüberprüfung auf Zelle mit Format hhmm

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
  Dim objRegExp As Object
  Dim mbrChoice As VbMsgBoxResult

  If Target.Cells.Count < 1 Then Exit Sub
  If IsEmpty(Target) Then Exit Sub
  If Target.NumberFormat <> "[hh]:mm" Then Exit Sub  

  Application.EnableEvents = False
    
  Set objRegExp = CreateObject("VBScript.RegExp")  
  objRegExp.Pattern = "^[-]*([01][0-9]|2[0-3]):[0-5][0-9]$"  
   
  If Not objRegExp.Test(Trim(Target.Cells(1, 1).Text)) Then
    Target.Cells(1, 1).Activate
      
    mbrChoice = MsgBox("Geben Sie die Zeit im Format [-]HH:MM ein.", _  
                       vbApplicationModal + vbCritical + vbRetryCancel + vbDefaultButton1, _
                       "Falsches Format")  
      
    Target.Cells.ClearContents
    If mbrChoice = vbRetry Then SendKeys "{F2}"  
  End If
    
  Application.EnableEvents = True
End Sub