Here's a short routine which can distinguish UserControls/ActiveX controls from intrinsic VB6 controls:

Code:
Private Function IsActiveXControl(ByRef Ctrl As Control) As Boolean
    On Error Resume Next
    IsActiveXControl = TypeName(Ctrl) = TypeName(Ctrl.Object)
End Function
Code:
For Each C In frm.Controls
    Select Case True
        Case TypeOf C Is TextBox, TypeOf C Is ComboBox, IsActiveXControl(C)
            'Do stuff
    End Select  'Unlike If, Select Case is able to short-circuit Boolean expressions
Next