This only allows you to bribe if you have money (the money "item" (actually a weapon) with classname EvMoney) and person has not been bribed before:
If you want to prevent anyone from bribing this guy again then in bribe.sqf or whatever you call your file that get's run you should set the "bribed" to true. This also frees you from having to deal with removing the actions over MP which can be tricky if you have not done it before:
this addAction ["Bribe", "bribe.sqf", , 1, false, true, "", " ""EvMoney"" in (weapons _this) && not (_target getVariable [""bribed"", false])"];
_target = _this select 0;
_caller = _this select 1;
//He cannot be bribed again - you probably want to remove the money from _caller too.
_target setVariable ["bribed", true, true];