Go to UnrealTournament\System\User.Ini (the file is a configuration file, use Notepad), then Find a Blank key or Keys ( For examples: R=,U=, or 7=), put the cheats you desired.

Here are 3 examples (I REPEAT,THIS ARE EXAMPLES):
U=AllAmmo
R=God
7=Loaded

Press the key you put it on a cheat, like U=AllAmmo,then at the game when you press U, all of your weapons ammo comes a total of 999 (This is an example, Not automatic).

Try it! Thanks to CheatingDome, That gave me the idea when I went to the Splinter Cell Cheats. I tried it and it works.