You can use screen_size.x and screen_size.y. To keep your panel in the bottom right, just use a loop like this:
Code:
while(1)
{
panel.pos_x = screen_size.x - panel.size_x;
panel.pos_y = screen_size.y - panel.size_y;
wait(1);
}
If the size of the panel depends on the size of a bitmap, and that code doesn't work (try it out first), you can use the size of the bmap:
Code:
while(1)
{
panel.pos_x = screen_size.x - bmap_width(panel.bmap);
panel.pos_y = screen_size.y - bmap_height(panel.bmap);
wait(1);
}