This is one of those low-tech, high-banger hacks to pretty-up your ASP.NET data when outputting to Excel. I posted darn-near a year ago on how easy ASP.NET makes it to output to native Excel. Consider this post as the 2005 enhanced version.
I had to update an ASP page this morning (last-modified in 2001 for a, um, budget conscious client) which output data to Excel. Working in ASP after four years is another story, but I won't bore you or myself with the painful details of that. The point is that I wanted to purdy-up the output which is where I came up with my hack.
Take your output report (in Excel), format it the way you want it and save it to HTML. Open the html file in Textpad (or whatever), copy the