From what you have described I think you could create this by using DataAssist and Security Assist together. The first thing to do would be to use The DataAssist Wizard to create a set of pages for administering the sales. These pages would be interacting with your sales table and allow you to insert, update, search and delete records from this table.
Once that is in place you can use the Security Assist wizard to generate the user login portion. The wizard will create a new user registration page, the login, profile and some other pages for the users.
After you have used both wizards you can go back to the results page that was created by DataAssist and alter the recordset on this page, you will want to filter based on the session variable that is set in the authenticate user server behavior that holds the user id. Finally you would use the Security Assist access page manager to apply a logged in access rule to these pages. This should give you a set of pages that the user must login to use, then the pages can be used to see the sales, and add new ones. The sales the user would see would be limited to their own based on the filtering of the results recordset.
Please post back with questions that you have and I can give you some more pointers or detail some of these steps further for you.
