as Excessus described: you need TWO vertex numbers, one of a vertex at the top of the cane and one at the bottom of it.

Code:

---

var whacking = 0; //at the top of your script

//... in your players while loop:
if(key_ctrl || whack_percent)
{
	whack_percent=(whack_percent+5*time)%100;
	ent_animate(me,"whack",whack_percent,ANM_CYCLE);
	
	var trace_from[3]; var trace_to[3];
	vec_for_vertex(trace_from,player,200); //replace 200 by your number
	vec_for_vertex(trace_to,player,300); //replace 300 by your number
	
	c_trace(trace_from,trace_to,ignore_me+ignore_passable);
	if(you != null && you.skill55==1234)
	{
		ent_remove(you)
	}
}

---

I doubt this will work, its just some pseudo code to give you an idea about trace.
By the way: Are you using A5 or A6? (the script above is written for A6)