Please have a look at the 2 subs below

Private Sub POLines_Change()
UpdateTransferButton POLines, AddPSLines
End Sub

Private Sub UpdateTransferButton(ByRef lb As ListBox, ByRef b As
CommandButton)
Dim index As Integer
For index = 0 To lb.ListCount - 1
If lb.Selected(index) Then
b.Enabled = True
Exit Sub
End If
Next
b.Enabled = False
End Sub

From the first subroutine, I'm trying to call the second one, which takes as
parameters a ListBox and a CommandButton. I'm getting a runtime error on the
call form the first subroutine indicating that I have type mismatch. Can
someone tell me why??

When I change the 2 parameters to Variants, everything is OK.

Why can't I pass a ListBox as a ListBox and same with a CommandButton

Thanks
Mike