Jeff, this same strategy will work with Designer Documents. The difference is in the particulars of the XFA Object Model (the actual functions and properties)
The following code is uesed to make subforms hidden/visible
xfa.form.form1.Pg1.Subform1.presence = "visible";
xfa.form.form1.Pg1.Subform2.presence = "invisible";
The word "hidden" can also be used, but don't do it. It forces the removal of the form fields from the document layout, whereas "invisible" just hides them from view.
Thom Parker
WindJack Solutions
www.windjack.com