[Jack_Leslie]

Make a check then.

At the top of your script:

pawn Код:

new gHasPlayerChosenSkin[MAX_PLAYERS];

Then have this for OnPlayerSpawn:

pawn Код:

public OnPlayerSpawn(playerid)
{
    if(!gHasPlayerChosenSkin[playerid]) {
        gHasPlayerChosenSkin[playerid] = 1;
        ShowPlayerDialog(playerid, 1, DIALOG_STYLE_INPUT, "Select your skin", "Please input the Skin ID you wish to use", "Select", "");
    }
    return 1;
}

Edit: As said above ^