Option Explicit
 
Private Sub Command1_Click()
 If Val(Text1.Text) > 0 Then
    Select Case Combo1.ListIndex
      Case 0
      Label1.Caption = Val(Text1.Text) \ 50 & " ml Öl"
      Case 1
        Label1.Caption = Val(Text1.Text) \ 33 & " ml Öl"
      Case 2
        Label1.Caption = Val(Text1.Text) \ 25 & " ml Öl"
    End Select
  End If
End Sub
 
Private Sub Form_Load()
 
  Combo1.AddItem "1:50"
  Combo1.AddItem "1:33"
  Combo1.AddItem "1:25"
 
  Combo1.ListIndex = 0
End Sub
 
 
Private Sub Text1_GotFocus()
  Text1.SelStart = 0
  Text1.SelLength = Len(Text1.Text)
End Sub
 
Private Sub Text1_KeyPress(KeyAscii As Integer)
   If InStr("1234567890" & Chr$(8), Chr$(KeyAscii)) = 0 Then
      KeyAscii = 0
   End If
End Sub