freeradius + sqlippool

Good afternoon! I have a question. It is necessary to assign ip-address by RADUIS-server to gprs user. My decision is to use freeradius+sqlippool for this purpose . But there is one problem. ippool name is initially unknown. It should be taken depending on a phone number. I.e. there is one more table in my database, where is a conformity - number (calling station id)=ip pool. (If calling-station-id does not present in the table  - RADIUS takes default ippool name.) Is there a good way to realize the similar scheme? Thanks for advices.