Intranet site design Qs (+Network sharing)

Hi all,
This is my first post to the Web Design forum and hope u all help me.

Scenario: I have designed an Intranet site and hosted in a Win2K server + IIS 5.0 and clients are all WinXP pro. And 3 types of users can access this site and they are created in this server. One is admin and the second is TL and the third is agents. The site is developed with ASP and MS Access.

Requirement: The agents can view data thru the web pages, but should not be able to view the data by accessing the folder in the server.

Issue: Right now the agents can open the folder by the Ip address of the server.

I read from somewhere that if we gave 'WRITE" permission to that folder for the agents then they will not be able to browse the folder or view any files, but they still can view the data thru webpage

Plz help me out