No, I can't get it to work properly, but I may have stumbled across something trying out your example. 

When I set the IncludeINFormEditType = DetermineByBusinessObject on the form, the FormEditingStateChanged event doesn't seem to fire, therefore the code to enable the button isn't executed. When I change the value to AllBusinessObjects or PrimaryBusinessObject, it does fire and the edit button is enabled, so my problem seems to be related to the DetermineByBusinessObject setting.

Does this help?

Thanks

Tim

Did you get it working? 

Thanks Ben.

This is the code that enables the edit button.  When the EditingStateChanged event of a business object is raised, this code is called.

            '-- Determine the edit button's visibility
            For Each loBO In Me.ParentForm.GetListOfEditBOs()
                If (loBO.Count > 0) AndAlso _
                        (loBO.EditingState = BusinessEditingState.Idle) Then

                    '-- Only enable the edit button if the business object has records and it's idle.
                    llEdit = True

                    '-- Bail after we find the first business object that needs the button
                    Exit For
                End If
            Next

So, try calling the GetListOfEditBOs() on the form and make sure that at least one of the objects in the list has a count of > 0 and is in the Idle mode.

I have a SF Maintenance Form with 3 business objects.  Two business objects are editable and the third, a BO based on a view, which is not (The third BO is used on a panel control to display information on a grid).  I set the IncludeInFormEditType = DeterminedByBusinessObject.  I then set the IncludeInFormEdit on the PrimaryBO and ChildBO = True, and False on the third BO.

The 'Edit' button on the MFTS is disabled...Did I mess a setting somewhere? 

I have tried various combinations but can't seem to get it working unless I change the IncludeInFormEditType setting to AllBusinessOjects or PrimaryBusinessObjects, which then causes problems on my third BO.

Thanks

Tim