Public Function istdopp(pruefstring As String) As Boolean
ReDim a(Form1.Grid.Rows - 1) As String
For x = 0 To UBound(a)
a(x) = Form1.Grid.TextMatrix(x, 4)
Next x
For Y = 0 To UBound(a)
If pruefstring = Form1.Grid.TextMatrix(Y, 4) Then istdopp = True: Exit For
Next Y
End Function
 
If istdopp(Text1.Text) = True Then MsgBox "Der Eintrag existiert bereits!": _
  Exit Sub