Doom 3 help

[64fanatic]

Okay, I've beat the game, and I wantto go back to certain levels, so I search doom 3 here on cheatingdome, and it states that if I bring down the console(using ctrl+alt+~, this works, i'ved used other cheats b4) and I type in "name of map".map it'll send me to that place, but it just gives me the "unknown command line" crap.

Does anybody know how to get this working???!!! Its sort of a nnoying when these certain "cheats" don't even work...