its even simpler than that. Using HTML you can just add this metatag to your page (first thing on the page):
<meta http-equiv="X-UA-Compatible" content="IE=7" />
If you wanted to do it using.net, you just have to send your http request with that meta information in the header. This would require a page refresh to work though.
Also, you can look at a similar question here: Compatibility Mode in IE8 using VBScript