Jim, If you receive 100% from the VA, it will not affect your retired pay at all, as you will get 100% of that too. Under the present CRDP prgram.
If you get a lesser percentage, then things can get a little complicated. Below 50% from the VA, and you are paying yourself. Since you will give up a corresponding amount from your Retired Pay. Just save a little on taxes, since VA awards are tax free.
Between 50% and 90%, you would need to check out the CRDP tables to see how much you would get, over and above the amount of the VA award.
For example, I retired in 1980, and until I reached the 80% disability mark, I was paying myself. Then CRDP was introduced eff. 1 Jan 2004, and the USAF finally started paying me some.
Another thing about the 100%, if you are 100% Schedular (means you have disabilities that actually total 100% under VA math) you will get full retired pay now.
If, on the other hand, you are 100% TDIU (that is granted Total Disability on the basis of Individual Unemployability; on the basis of Service Connected disabilities), then you will have to wait until 2009 to get 100% of your Retired Pay, until then it is phased in each year, for this category alone.
Everybody else, below 100%, their CRDP, if it survives the Republican's attempts to do away with it altogether, will have to wait until 2014, until they recover their full Retirement Pay.