How can I do CCBill Data Link

Hello,
Can anybody Help ME…

I have integrated ccbill for My new site.And It has success fully aupdating the database Through Approve POST URl , but my problem is how to send request to datalink.

That is if the selected transaction is for 1week or 1 month then how can we know that the time is expired or has the member made a transactin again…? if the member not made a transaction then I have to downgrade his membership…

Please help me. if anybody could understand my problemm…
Otherwise please let me know I will explane you more…
Thanks,
Bejoy