set() and reset() are your friends

Code:

---

PANEL* start_pan = 
{
	layer = 10;
	pos_x = 20;
	pos_y = 60;
	button (22,22,"DS_ss_button_1.bmp","DS_ss_button_2.bmp","DS_ss_button_1.bmp",load_start,NULL,NULL);
	digits (50,25,4,start_font,10,start_button); 
	button (22,62,"DS_ss_button_1.bmp","DS_ss_button_2.bmp","DS_ss_button_1.bmp",load_start,NULL,NULL);
	digits (50,65,4,start_font,10,load_button);
	digits (10,30,4,start_font,10,startpan_hide); 
	flags = VISIBLE;
}

function main()
{
	video_mode = 7; 
	mouse_map = mouse_bmp;
	mouse_mode = 2;
	level_load("mainmenu.WMB");
	wait (1);
	/////////////////////////////////// camera set for mainmenu
	vec_set(camera.x,vector(-123,-123,-103)); // place the camera at X,Y,Z
	camera.pan = 77;
	camera.tilt = 15;
	camera.roll = 0;
	set(start_pan, VISIBLE);
	
	while (1)
	{
		mouse_pos.x = mouse_cursor.x;
		mouse_pos.y = mouse_cursor.y;
		wait (1);
	}
}

function load_start()
{
	camera.x = 200;
	level_load("level_start.WMB");
	reset(start_pan, VISIBLE);
	wait(1);
	
}

---