Need help transforming %3F into ? and %3D into =

I have a number of inbound links that contain entities which result in 404 errors. I would like to create some url rewrite rules (IIS7) to take care of this. These rules need to work on any page since some of the links that contain entities could be several folders deep and be a file other that index.php.

For example the rewrite rules should be able to handle :

http://www.mysite.com/index.php%3Fpage%3Dtest

http://www.mysite.com/folder/somepage.php%3Fvariable%3Dtest

and convert them into:

http://www.mysite.com/index.php?page=test

http://www.mysite.com/folder/somepage.php?variable=test

Any help I can get on this I would appreciate as my knowledge in IIS URL Rewrite is pretty limited. I did find this post (http://forums.iis.net/t/1185938.aspx/1) which may help a bit.

Thanks for any replies