how can i prevent my user in one site about financial report in other sites

Hi

we implement our project in 4 sites via Citrix and all of users works on head office database, we used Document Series to divide evey site financial/inventory/procurement transaction . for example one site's JE number start 1 to 1000000 and other site start form 1000001 to 2000000 . but we see all user can see financial report like TRial balance, General ledger for other site but selecting in extend option in report without viewing them in detail. How we can make constrain for this issue, I mean user in other site cannot see other JE in General ledger report by selecting documnet series in Extend option.

thansk