Dynamically Updating List/Menu from previous Menu

I need to update the content of a list/menu with values derived from a database...unfortunately, the database query is initiated from a previous list/menu, which in turn is populated from a list/menu rewrite. In other words, I have 3 menus...the first has static values...the second is written by selecting a value in the first and is empty until the rewite takes place....the 3rd needs to take values from the 2nd menu and then query the database and update itself.All 3 menus are contained within the same form. Am I asking the impossible? If anyone can help to achieve this, I would appreciate it.

Thank you