How about you forget the lockwp thingy and simply use a condition.
put in your radio triggers 'on activation' line
tanksgogo=true
then create 2 waypoints for the tank group
1st right on top of the leader tank
2nd to the place where you want them to go after the radio call
then put in the 1st waypoints 'condition' field
tanksgogo
and there you have it. The tanks won't move untill the condition 'tanksgogo' is set to true by the radio trigger.