Time based billing

Hi all, I want to ask that if there is some kind of flexibility in freeradius to have time based billing. I want a customer to be charged at different rate at different time. Like I want to introduce a package which has different rate at morning eg. $1/hr from 0800 to 1200 then 0.5/hr from 1200 to 1800 then 0.25/hr from 1800 to 0800hrs. Now what should I do. I know that there are sqlcounters but these are for flat rates. Now is there any flexibility to do so. And if not then is there any plugable module available by which i could achieve this. I'll be thankful for your help Regards, Saeed Akhtar