a physbox trigger

hello guys, i wonder if u can help me with this.

i was in a middle of hl2 map, and i was trying to create a kind of physic object that shuld trigger a trigger when it fell ( this case it is a "func_physbox")
my problem is that every physic object trigger the trigger, even grenades.

so how do i make so only a specific object trigger the trigger (in this case it is a "func_physbox")
if it is even possible.

ty

name your physbox and have that trigger. .. .
note though that HL2DM phyboxes are a pain in game.

i have named my physbox, i just don't know how i make it, so only the physbox to trigger it.
i've looked through the trigger func's, but i haven't been able to find anything that only activates on the specific object

ty very much . now it works