Private Sub Command1_Click()
  Dim A as Long
  A = Berechnen(CLng(Text1.Text), CLng(Text2.Text))
End Sub
 
Private Sub Command2_Click()
  B As Long
  B = Berechnen(CLng(Text3.Text), CLng(Text4.Text))
End Sub
 
Private Function Berechnen(Wert1 As Long, Wert2 As Long) As Long
 Berechnen = Wert1 + Wert2
End Function

Gruß
Marcus