URL Rewrite to replace some text in query string

I am hosting a legacy website in IIS7 and I have the URL rewrite module installed. The URLs are written in such a way so as to avoid using ?, & and =.

It does this by replacing the following:

? with -Q-
& with -A-
= with -E-

So for example a URL could be written as:

www.mysite.com/index.asp-Q-val1-E-100-A-val2-E-200

I would like a URL Rewrite rule to change the above to:

www.mysite.com/index.asp?val1=100&val2=200

Please provide the actual XML rewrite rules.