Quote:

if you did it and have some code that make a panel always be at the center of the screen (even if the player change resolution) please show me. Thank you!

Pretty simple.
All you need is the panels bitmap width and height and the screen size values:
 Code:
function pan_center(_pan, _bitmap)
{
  _pan.pos_x = (screen_size.x - bmap_width(_bitmap)) / 2;
  _pan.pos_y = (screen_size.y - bmap_height(_bitmap)) / 2;
}

// TESTING:
bmap my_bitmap = <my_bitmap.tga>;
...
panel test_pan { bmap = my_bitmap; ... }
...
pan_center(test_pan,my_bitmap);

PLEASE NOTE: This is rather pseudo code and written down from the top of my head. Not sure if it works, but it should give you an idea how to solve your problem.