Rebuild a web app (ASP)

A few months ago, I had a web application built, for managing customer leads. The point of the app was that a salesperson would key in every customer who visited our retail store, and mark if the sales process was successful, unsuccessful or the case is still open. If the case (lead) is still open, the salesperson needs to key in comments and next contact date with the customer. The original request for the app is in the attachment just for reference. The app was already built and is running on a company server. There are some mistakes in the app which need to be corrected and some additional functions that need to be added. The problem is that I cannot reach the original programmer and I DO NOT HAVE the source code file, so I basically would need the app built again (I think). If you can use any of the files of the current app, you should. The selected programmer can get the access to the active server wwwroot and the MS SQL DB (it is on the company intranet so it is not publicaly available. When app is completed, I will need you to install the app on the active server and transfer all the data from the exiting app to the new one. Once this project is completed I will have further add-on projects connected to this app.