1) Launch Arma 3, in vanilla, or with any mod (tested with All In ArmA Terrain Pack v1.2.1)
2)Go to Mission Editor
3) create a BLUFOR Player
4) Create a Flag
5) Create a trigger named Trig1 on the Flag; no sync, no group needed
6) Set the radius of Trig1 on 5m (square or Circle)
7) no timer
8) no text
9) Type: NONE
10) Activation: BLUFOR
11) One Time or Repetition (no influence on Looping Execution)
12) "Is Present"
13) condition: {(isPlayer _x) and (alive _x)} count playableUnits == {(isPlayer _x) and (alive _x)} count list Trig1;
14) On Act.: hint "test OK";
15) On Deact.: hint "test echec"; (like failed, in French)
16) (optional) Add a musique to the event on Effect Tab, in order to hear the loop