This might help. Use a gamelogic waypoint loop with scripting commands to keep trigger1 over the convoy. You'll need to initialise your variables in init.sqs and add whatever you want to happen when the trigger is fired. This is an example taken from a working mission: adapt the waypoints for your own purposes.
move <---- switch trigger 2
guard
move <----- switch trigger 1
S&D
cycle
trigger2
Activation: bradleyGuardGuard
On Activation: bradleyGuardGuard=false
trigger1
Activation box: detected by repeatedly
On Activation: as you like
On Deactivation: bradleyGuardGuard=true;
The waypoint sequence can be repeated as often as necessary, controlled by the triggers.
When the variable bradleyGuardGuard goes true the first trigger fires and the group goes to the guard waypoint. The variable is reset to false, ready for next time. The group sits on that guard waypoint with the detected by trigger over them, and when it fires they go to seek and destroy. When that trigger deactivates, that is they lose the enemy, then the first trigger fires again and they go back to the guard waypoint.
I told you triggers and waypoints were more powerful than most people think.