Username/password form

I wish to create a mechanism where a user logs into a workbook, and gets different data depending on his/her username. Is there a way to create usernames/passwords in Excel in a secure manner, without storing them plain text on a hidden sheet ? Are there add-in controls for this ? Recommendations ?

ie: user opens workboook and is prompted for a unique username and password. Otherwise, workbook either wont open, or defaults to lowest access level.

Thanks.