Use Mr Peanut system if you have a clear idea of which tanks may be involved (their names), if not, you may use something like this:
//fleeingcheck.sqf
_fleeingpos = _this select 0;
_fleeingradius = _this select 1;
fleeingsuccess = false;
_numfleeing = 0;
_tanks = [];
while {_numfleeing < 2} do
{
_tanks= _fleeingpos nearObjects ["Tank",_fleeingradius];
if (count _tanks > 0) then
{
_numfleeing = {((count crew _x) > 0) && (side _x == east)} count _tanks;
};
};
fleeingsuccess = true;
You may run fleeingcheck.sqf from your init.sqs file this way:
;init.sqs
[getMarkerPos "mk_fleeingcenter", 1000]execVM"fleeingcheck.sqf"
Then you may use global var fleeingsuccess in your trigger to check if enough tanks did reach the fleeing area.