The primary negative impact on your credit reporting comes from your missed/delinquent payments, if any, not from the "event" itself (short sale transaction) and there is absolutely no negotiating of that.....the lender will report your missed payments and the credit bureaus will determine how they calculate your scores, period. Generally, if all else is good, it takes 3 years to re-qualify for a mortgage loan, unless there are some extenuating special circumstances. I have heard of 1 lender who will qualify you immediately post short sale if you have NOT missed any payments during the process, but have not actually seen it done.
"Lester the Lister"
CDPE (Certified Distressed Property Expert)