Code:
/////////////////////////////////////////
#include <acknex.h>
#include <default.c>
/////////////////////////////////////////
BMAP* back = "background_01.bmp";
BMAP* back2 = "background_02.bmp";
BMAP* menu_back = "menu_back.bmp";
BMAP* on = "on.bmp";
BMAP* off = "off.bmp";
BMAP* over = "over.bmp";
/////////////////////////////////////////
PANEL* back_pan =
{
	bmap = back;
 	pos_x = 0;     
 	pos_y = 0;    
 	layer = 10;
	flags = OVERLAY | VISIBLE ;
}
PANEL* back2_pan =
{
	bmap = back2;
 	pos_x = 0;     
 	pos_y = 0;    
 	layer = 9;
	flags = OVERLAY | VISIBLE ;
}
PANEL* TIMEs_pan =
{
	digits(580, 300, 2, "Arial#150b", 1, sys_seconds); 
	flags = SHOW;
}
PANEL* TIMEm_pan =
{
	digits(580, 300, 2, "Arial#150b", 1, sys_minutes); 
}
function switch_min()
{
	reset(TIMEs_pan, SHOW);
	set(TIMEm_pan, SHOW);
}
PANEL* menu_pan =
{
	bmap = menu_back;
	pos_x = 128;
	pos_y = 128;
	button(256, 256, "off.bmp", "on.bmp", "over.bmp", switch_min, NULL, NULL); 
	flags = SHOW;
}
function main()
{
	video_mode = 10;
	screen_color.red = 150;
	mouse_mode = 1;
	while(1)
	{
		wait(-1);
		set(back_pan,SHOW);
		wait(-1);
		reset(back_pan,SHOW);
	}
}

Does not work. No it shows one problem more: "off.bmp not found" but it´s in the folder. and it still shows the butten problem...