I don't understand completely. You have a formclass with a treeview control right? The object .TreeMenu is a property of the form? There is no treeview control on the toolbar, correct? So THIS refers to the form not the toolbar, correct? If so, how did you instantiate the form? Is there an object reference for it so you can change it to something like

*Instantiate form
DO FORM myform NAME oform
*Toolbar button click
IF TYPE('oform')="O" .and. !ISNULL(oform)
   WITH oform
	.TreeMenu.HEIGHT = (.HEIGHT - 15)  && The treeview
	.TreeMenu.WIDTH  = (.WIDTH  - 25)
	.TreeMenu.TOP    = (.HEIGHT - .TreeMenu.HEIGHT) / 2
	.TreeMenu.LEFT   = (.WIDTH - .TreeMenu.WIDTH) / 2
   ENDWITH
ENDIF

Sorry if I misunderstood completely.

>On a formclass with a treeview control this works perfectly fine:
>
>

>WITH THIS   && The toolbar
>	.TreeMenu.HEIGHT = (.HEIGHT - 15)  && The treeview
>	.TreeMenu.WIDTH  = (.WIDTH  - 25)
>	.TreeMenu.TOP    = (.HEIGHT - .TreeMenu.HEIGHT) / 2
>	.TreeMenu.LEFT   = (.WIDTH - .TreeMenu.WIDTH) / 2
>ENDWITH
>

>
>On a toolbar it does zilch. Why?
>
>BR & TIA