Any way to collect network usage data for dial-up subscriber

NANOGers , is there anyway for AAA to get special online subscriber usage information without enable interim accouting on BRAS? Reading through RADIUS protocol , it seems that if we want to get online subscriber information enable interim accounting on BRAS is the only way . But, if enable that on BRAS ,, all online subscribers accouting infromation will be reported periodically. that will generate too much load on AAA , and we need to monitor a small set of subscribers only. thanks in advance. joe sun