Have your users make spreadsheets online, no excel needed
Now first off, this places a DataTable into the Session State, and I know some people have a problem with that... I don't care. Now that that is out of the way, I can explain how this works.
It is very simple, this program runs through all of the TextBoxes and DropDownLists that you have within the input_container Panel and adds them as string columns to a DataTable dt. Once that is done, each entry is simply added to the DataTable and rendered onto a GridView. Then I use Matt Berseth's GridViewExportUtil to spit the spreadsheet out to the user. Everything is taken care of real-time with no writing to the disk. Pretty simple.
I also included a way to edit as a normal method wouldn't work in this case, it just populates a DropDownList every time you add a new item and pops it back into the forms if you choose to edit it _but_ if you do not save, the record will be lost (there is a warning).
Another thing to note is that this is a drop-in-and-use application. Everything is populated automatically, you need to do absolutely nothing to the code-behind in order to use this utility, just customize your fields in the default.aspx in the input_container and the rest of the work is done for you. I used my method of parsing IDs of the input fields to make column names so ddlLets_Party turns in to a column "Lets Party", Last_Name becomes "Last Name", strFruit becomes "Fruit" and so on. You could easily add another attribute as ColumnName or something like that if you please.
Here is the provided example: Excel Spreadsheet Builder In Action, and the code: