a bit vauge, but it sounds like you want to make it so the collision area is larger than the model. You can define that the old fashioned way, like in Pong. You know:

if ( ent_pos_X > panelLeftSide && ent_pos_X < panelRightSide
&& ent_pos_Y > panelTop && ent_pos_X < panelBottom )
{
panelName.pos_x = whatever ;
panelName.pos_y = whatever ;
}

OR

instead of a panel, you can use:
ent_create( "myImage.tga" , vector ( 400,0,0 ) , 0 ) ;

Now your bmap is an Entity with all the built in collision detection, etc.