_nearBuilding = (nearestBuilding player);
_numDoors = getNumber (configFile >> "cfgVehicles" >> typeOf _nearBuilding >> "numberOfDoors"); 

//now, you can make a loop with _numDoors
for "_indx" from 1 to _numDoors do {
    _doorAnimName = format ["door_%1_rot", _indx];
    _nearBuilding animate [_doorAnimName, 1];
};