yep....
name the gate.
put a trigger around the gate area (i used 2x2)
for the trigger:
-make sure you make it trigger via east, west or anybody
-make sure you make it activate repeatedly
-make sure you enter the following into your on activation field:
gatename animate ["arm", 1]
-make sure you enter the following into your on deactivation field:
gatename animate ["arm", 0]
obviously, replace the above gatename with whatever you named the gate.
hope that'll help!
;D