What do you mean "JSP table"? Are you talking about a html element called <table>?
In that case, there's nothing JSP specific. If you know how to parse html in C#, that's it.
If you were talking about JSP outputting something that can be readily imported into Excel, well, that's doable too, but you'd have to know the format. If csv is enough, go with that.
If you need real Excel export, look at Seam, it has excel export freature:
http://myjavaroom.blogspot.com/2009/10/microsoft-excel-spreadsheet-in-jboss.html
http://myjavaroom.blogspot.com/2009/12/jboss-seam-excel-implementation-part-2.html
Looking further into that would be waaay beyond this topic and forum.