First! open up the Cheat Table with Cheat Engine. This is done by dragging the CT over a shortcut for Cheat Engine.
Second! Open up AVA! (Log in and all that good stuff)
Third! Link CE to the AVA process
Fourth! Go into death valley extreme first so you can become more familiar with how this process works.
Note: this can be used on ALL co-op missions, all you need to do is be in a game and not dead.
Fifth! Switch to cheat engine and down the bottom of that window there is a button with "Advanced" on it. Click that. There, double click the thing labeled "box". You should be taken to a screen full of hex, or random code. You want to right click the value at the top of this table. DO NOT SCROLL UP AT ALL, IT WILL BE THE TOP THING YOU SEE. After you have right clicked this value you want to go to "see what addresses this affects" (or something very similar, it should be towards the bottom of the drop down box). It should ask you to inject something into AVA, click yes and another, smaller, window will come up. Double click on the value in that window and tab back into your cheat engine. YAY! you have a value that you can alter. Since your in DV:Ex change this value to 4.
Note: After every game the value you altered will change and will no longer be the box value, you will have to go back to your smaller screen and double click on the value below your last one. These should start at 0.
You do the exact same thing but with the address below "boxes". However, this does not grant exp or supply; or any bonus' at all; and can only be used for an effect in BG. When in BG you will have to change the value to 4 and complete the first round to skip to round 5, then you have to complete the last round regardless. So, it is pretty useless changing the round value.