Something

exten => _X.,1,set(db(stupidgroup)=$[${db(stupidgroup)}+1])
exten => _X.,2,gotoif($[${db(stupidgroup)}>2],4,10)
exten => _X.,4,Busy()
exten => _X.,10,Dial(zap/g1/${EXTEN})
exten => h,1,set(db(stupidgroup)=$[${db(stupidgroup)}-1])