Have mw3 in windowed mode so you can see cheat engine and mw3 side by side. Then go to cheat engine and find memory view in the bottom left right click on the hex and go to address. Type in 01ccfaaa. Then you will see your custom classes. Find the one you want to change. Go on mw3 and select a random prof and you will see on cheat engine that it will flash red and change. Go to that value double click it and type 140 for damage.