[Konstantinos]

I will make it easier for you to understand what Vince meant.

pawn Код:

// global:
new Player_Name[MAX_PLAYERS][21];

#define GetName(%0) Player_Name[%0]

// OnPlayerConnect:
GetPlayerName(playerid, Player_Name, 21);

Now, replace "GetPlayerName(playerid)" with "GetName(playerid)" and you're done.