Edit Word Documents On-line & Save To DB

I need to develop a web application using asp, which ideally should do the following

1. Generate a word document combining templates with dynamic data from a sql server. (I was thinking about generating xml docs)

2. Let the user see and modify the generated document on-line, from he browser

3. Save the (possibly) modified document to a table in SQL server.

I already know how to download/upload files, and save them into a DB.

The problem is I would like to automatize the whole thing, and not forcing the user to download the file, open, edit, save and finally upload.

Any idea would be appreciated.

PS: Even more ideal would be to come up with a general solution, in order to be able to open any kind of doc with the right app, and then automatically post it to my app. Or maybe someway to allow to edit it right from the server.