[Zh3r0]

Use a timer and something like this:

pawn Код:

forward ChangeMode();
public ChangeMode()
{
   switch(random(3))
   {
        case 0: SendRconCommand("changemode GM1");
        case 1: SendRconCommand("changemode GM2");
        case 2: SendRconCommand("changemode GM3");\
   }
}

//When scripts tarts
SetTimer("ChangeMode", 10 * (60 * 60), 0); //Change 10 with your minutes.