casparas,
May I make a suggestion about your programming style?!

It's YUK!
Use an array of text boxes
you can then do this:
Code:
Private Sub txt_Change(Index As Integer)
Dim i As Integer
For i = 0 To txt().UBound
  If Not IsNumeric(txt(i).Text) Then
    txt(i).Text = 0
  End If
Next i
 
txt1234.Text = Plus(Val(txt(0).Text), Val(txt(1).Text), Val(txt(2).Text), Val(txt(3).Text))

End Sub


------------------
Mark Sreeves
Analyst Programmer

[email protected]
A BMW Group Company