Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
If Not Intersect(Range("G4:AE72"), Target) Is Nothing Then
If IsNumeric(Target.Value) Then
If Target.Value = CInt(Target.Value) And Target.Value < 100 Then
If WorksheetFunction.CountA(Range("G" & Target.Row & ":AE" & Target.Row)) > 1 Then
MsgBox "schon ein Wert vorhanden"
Target.Value = vbNullString
End If
Else
MsgBox "Falscher Wert"
Target.Value = vbNullString
End If
End If
End If
Application.EnableEvents = True
End Sub