[Rizard]

Without looking at your code, yes there certainly is a way to block the spawning.

pawn Код:

public OnPlayerRequestSpawn(playerid)
{
  if(playerlogin == true) //will give errors but you have to create your personal statement here.
  {
    SendClientMessage(playerid,0x00FF00FF,"Logged in succesfully!");
    return 1;
  }
  else
  {
    SendClientMessage(playerid,0xFF0000FF,"You must login before spawning");
    return 0;
  }
}

If you don't have any clue howto do this in your script , let me know.

Grts Riz