make a two man team in editor, make team leader player and other member playable. somewhere away from the team create an enemy force an AI has no chance against and press preview. now send the AI to the location of the enemy force but do not follow, wait in safety where you cannot see him. before you automatically ask for sitrep and when you are sure he's dead switch to him using 'F2' and 'Switch To Unit 2'. Now you are stuck, you will have to close arma 3 down.