Question about manual exposure mode on the 5D MK II

Dear 5D MKII experts,

I would like to be able to fix the speed and the exposure at a desired value (it's basically what the manual exposure mode does) and then to be able to increment or decrement by 0.3EV step the exposure. Or in others words, combine manual exposure mode and exposure shift/correction fonction.
Do you think it is possible ?
Thanks for your help.