you need panel with window
Point is that window shows only a part of the bmap.

(example bmap)
Code:
bmap your_bmap = "some.bmp"; //it could be some frame with black inside but not necessary
bmap health_bar = "health.bmp"; //bmap with width f.e. 200 where only half of bmap is till with some color rest is black, height of this image is f.e. 10
var my_live;
panel show_health
{
bmap = your_bmap;
window 0,0,100,10,health_bar,my_live,null; //read help
flags refresh, overlay;
}
then you may convert your live to % like:
Code:
my_live = (my.live * 100) /my_max_live;
my_live = 100 - my_live;
always 100 pixels of the bmap will be shown, but starting point will be change.
It means if you have 100% live then my_live = 0; it means that bmap will be shown from 0 to 100 of his width (bar will be full).
But if you'll have 60% of my.live then 100-60=40 so window will show your bar from 40 to 140 pixels so you'll see only part of color bar and rest will be invisible because rest is tilled with black color.
It's easyer to do than to explain in english

Read help