Is it possible to make a hit detection system?

I was messing around in GameMaker and saw a function titled 'Collision_ellipse'. I was wondering if it was possible to use this to made a 'hit box' for the head of a player. Basically positioning the ellipse to that it covers the players head, and detects collisions, im pretty sure you would have to disable collision checking for the original sprite too. I want to be able to make multiple hit boxes so creating a new sprite for each is out of the question. I think i want something like this: a collision check that can be called AND defined within a script. i.e.    (my made up function)    collision_check_rectangle(x1,y1,x2,y2,obj)  where 'obj' is the object to check a collision with  so collision_check_rectangle(20,30,20,30,obj_bullet)  would check for a collision with obj_bullet at position 20,30,20,30. I hope i was specific enough, and if i wasnt please let me know. thanks in advance, -TheHerbalist

to demonstrate the amount of tags (what i like to call them) i need, here is the list... remember multiply these * amount of players...

tag_head tag_neck tag_uppertorso tag_centerofmass tag_lowertorso tag_lshoulder tag_lupperarm tag_llowwerarm tag_lhand tag_rshoulder tag_rupperarm tag_rlowwerarm tag_rhand tag_pelvis tag_lthigh tag_lcalf tag_lfoot tag_rthigh tag_rcalf tag_rfoot tag_weapon