I actually have a similiar question, but am not positive of the answer. I requested for some schools and realized that I have other preferences instead, so I wanted to switch the schools. I checked on the ADA website and this is what it says (http://www.ada.org/prof/ed/testing/dat/index.asp)
"Requests for score reports after the test are subject to delay and additional expense. Once an application has been submitted, no score report request changes will be allowed."