Any way to have a form implement and interface?

[LaVolpe]

Hmmm. You can create an interface class containing the function stubs. Each MDI child will implement that interface. Then to call a specific MDI child's interface, the logic would look something like...

' iCustom interface
Option Explicit
Public Function ObjectPointer() As Long
   ' stub
End Function

' each child form
Implements iCustom
Private Function iCustom_ObjectPointer() As Long
    iCustom_ObjectPointer = ObjPtr(Me)
End Function

' the MDI parent
Dim theInterface As iCustom
Set theInterface = Me.ActiveForm
Debug.Print theInterface.ObjectPointer, ObjPtr(Me.ActiveForm)

Don't kow if you already had this? If not, then is this what you are looking for?