write a function, and call it everytime you change the resolution.

like


void vCenterPanels(){
panelname.pos_x = screen_size.x/2 - bmap_width(panelname.bmap)/2;
panelname.pos_y = screen_size.y/2 - bmap_height(panelname.bmap/2;
..
}

or something like

void vCenterMe(PANEL* p){
p.pos_x = screen_size.x/2 - bmap_width(p.bmap)/2;
p.pos_y = screen_size.y/2 - bmap_height(p.bmap/2;
}