I have a template for an invoice. It just has placeholders for all of the
information I need to save to it.

I'm working in an asp.net environment (using VB) where I need to
programmatically generate invoices.

I need to copy the template spreadsheet and then modify the copy.

What's the code that I'll need to do this?

Also, given that the web app is multi-threaded, what do I need to keep in
mind to be sure that multiple invoices can be created simultaneously? Do I
have to worry about multiple instances of excel opening up?

I'm really a total noob with office programming. So forgive my dumb
questions. Your help will be GREATLY appreciated.