I tried doing this:

Code:
#define BEND_WAIST    skill17

...

action player_code()
{
	...
	
	ent_bonename(me, "waist", 194);

	my.BEND_WAIST += 5 * mouse_force.y;
	ent_bonerotate(me, "waist", vector(0,my.BEND_WAIST,0));
	
        ...
 
        while(1)
        {
           ...

            wait(1);
        }
}


...but no such luck. The waist is not bending forward or backward when I move the mouse up or down.

I also get a pop-up error message that says:

Code:
Error E1515
Invalid function arguments in player_code
OK             Cancel