You could use a trigger placed at a point just prior to the gate, set Activation to whatever side you want to open (or close) the gate, group it (F2 and drag a line from unit to trigger) to the unit that willl open gate, then put this in the onActivation line:
(object NUMMER) animate ["Component02", 1]
to open or
(object NUMMER) animate ["Component02", 0]
to close the gate.
You will need to enable "Object IDs" in editor and replace the "NUMMER" (without quotes) with whatever the object ID number is on the map.
When the unit comes into the trigger zone, the gate will open or close.
Wadmann