I also use top level forms.
At the beginning of app, I store a reference into an application object property. Then is possible to call form methods using that reference
In init()

oApp.MainFormRef = this

then you can

oApp.MainFormRef.ChangeHeading()

Or use a global variable which store top level reference

>I have designed a menu with the menu builder. From my top level for, I am activating this menu with
>

>DO gl_menu.mpr WITH THISFORM, "MainMenu", .T.
>

>Upon selecting the menu item, I want to access a method written in the top level form. If I write the procedure code for the menu item as

>THISFORM.ChangeHeading

it says ‘THISFORM can not be used within the method’.
>What do I need to do access a form method or any other control on the form?
>
>Thanks in advance.
>Yashodhan.