Urgent Please help.

one of company in Qatar issued employment visa for my friend and now he got the better offer in Dubai.(now he is India)
If he goes to Dubai then what will happen for Qatar visa. if he want to come again to Qatar what will happen? his passport will be block listed? or he can enter without prob? since he did not enter Qatar with employment visa please advise... very urgent.
let him go to Dubai.
no blacklisting of passport or anything