Thats exactly what i used:

Code:
 
pos_x = (screen_size.x - bmap_width(myBmap))/2; 
pos_y = (screen_size.y - bmap_height(myBmap))/2;


as written in the manual, but i still get the error!!
does it have anything to do with versions or updates?

Upon my end shall I begin? Forsaking all I've fallen for.. I rise to meet the END!!