IWP and reports don't go well together. A lot of layout design options that work in Regular FileMaker don't work in a web browser. You may want to generate such reports as PDF's and insert them into container fields using Regular FileMaker and then your sales personnel can use their web browser to find the record for their and only their sales report for the time period specified.
If each salesperson logs in with their own account name and password, you can use this info to limit their access to just the records you want to allow them to view.
See "Editing record access privileges" in FileMaker Help and check out this particular sub section: "Entering a formula for limiting access on a record-by-record basis" for a description of how to set this up.