Button press is as simple as:
GTBU_Pressed	EQU	GT_TagBase+68	; ti_Data is boolean.
		; Set to TRUE to programmatically press a BUTTON_KIND
		; gadget, to FALSE to unpress it.  This is intended
		; for keyboard equivalents only!  DO NOT USE THIS
		; TAG TO TURN A BUTTON GADGET INTO A TOGGLE GADGET

    struct TagItem *ti;

    if (ti = findGTTagItem(GTBU_Pressed, taglist))
	{
	SelectGadget( gad, win, req, ti->ti_Data );
	}

