The following cheats will allow you to unlock any mission of your choosing in the mission select screen. Bring down the console with the tilde key (button to the left of "1") in game and type the following commands to unlock your desired mission sets.

Cheat - Effect
/seta mis_06 9 - Unlock "Rommel's Last Stand" Mission Set
/seta mis_07 9 - Unlock "D-Day" Mission Set
/seta mis_08 9 - Unlock "The Battle For Caen" Mission Set
/seta mis_09 9 - Unlock "Hill 400" Mission Set
/seta mis_10 9 - Unlock "Crossing The Rhine" Mission Set
/seta mis_05 9 - Unlock "The Tank Squadrons" Mission Set
/seta mis_04 9 - Unlock "Fortress Stalingrad" Mission Set
/seta mis_03 9 - Unlock "Not One Step Backwards!" Mission Set
/seta mis_02 9 - Unlock "The Battle Of El Alamein" Mission Set
/seta mis_01 9 - Unlock "The Winter War" Mission Set