Need Help Making COD4 Trouble In Terrorist Town Mod (TTT)

so im currently stuck on code where i want the game to randomly select the terrorists, randomly select the innocents, and the same for detectives. I cant find a code for randomly selecting or going on chance, or percentage... I want the game to completely randomly select a player, by chance, again... completely random. so basically what i want is a peice of code which lets me randomly select something.
e.g
40% chance goto thread Terrorist();
20% chance goto thread detective();
40% chance goto thread Innocent();
i hope you get the idea. thanks for reading and please post a reply