Private Function Quersumme(ByVal sText As String) As Long
  Dim lSumme As Long
  Dim i As Integer
 
  lSumme = 0
  For i = 1 To Len(sText)
    lSumme = lSumme + Val(Mid$(sText, i, 1))
  Next i
 
  Quersumme = lSumme
End Function

MsgBox Quersumme(Text1.Text)