Create editing form

I have a form that has a structure that changes according to choices the user makes in the form, and then submits into a db. I would like to transform that that form into an editing form, which means when [login to view URL] is calles with ?idStations=3, it will extract the data in the db where idStation=3, and will enable to edit it. Because of the changing fields according to users choices, the form will need to extract these choices from the db, and show the complete form accordingly. This is only for JavaScript experts as the JavaScript is complicated here, that's why the budget is high.