[Scenario]

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if(newkeys & KEY_CROUCH) // checks to see if playerid pushed C
    {
        if(GetPlayerInterior(playerid) == 0) cmd_enter(playerid, ""); // is their interior equal to 0 (meaning they're outside)? If so, perform the /enter command
        else cmd_exit(playerid, ""); // otherwise, perform the /exit command
    }
    return 1;
}