Private Sub Worksheet_Change(ByVal Target As Range)

Dim rngZelle As Range
Dim rngIntersect As Range

Set rngIntersect = Application.Intersect(Target, Range("AD8:AI" & Rows.Count))
If Not rngIntersect Is Nothing Then
      Application.EnableEvents = False
      For Each rngZelle In rngIntersect.Cells
          If IsNumeric(rngZelle.Value) Then
          If IsNumeric(rngZelle.Offset(, -22).Value) Then
              With rngZelle.Offset(, -22)
                  .Value = .Value - rngZelle.Value
              End With
          End If
          End If
      Next
      Set rngZelle = Nothing
      Application.EnableEvents = True
End If
Set rngIntersect = Nothing
End Sub