[blank.]

(With ZCMD)

pawn Код:

CMD:test(playerid,params[])
    {
    new Float:X,Float:Y,Float:Z;
    GetPlayerPos(npcid,X,Y,Z);
    if(IsPlayerInRangeOfPoint(playerid,5.0,X,Y,Z))
        {
        // The player is near the specified NPC, do your stuff here.
        }
    return 1;
    }

Of course range can be whatever you want it to be, I just set it to 5.0 here for the example.
Needless to say you need to know the player id of the NPC, denoted as 'npcid' in the example above.