Excel (and ASP.NET)

[Guy]

I'm developing an ASP.NET application that needs to process Excel files that
users can post on a shared directory on the server. These Excel files, that
need to be processed by the ASP.NET (C#) application, have the all the same
format. My question: is there a way to have a kind of "template" to validate
the posted excel files against. This to void that someone can post any kind
of Excel file.
What I'm looking for a way for Excel, what an xsd does for an xml file.

Any suggestions?
Thanks