cookieless session brackets being changed to entities

Hi all

We have a process on our site which takes our users to a remote site to perform some actions, which then sends the users back to our site. We send the link we want the remote site to send the users back to as part of the request, ie I send over "http://mypage.com/(Sadkasdfljsadfasd)/page.aspx

The problem we have discovered is that the remote site is replacing the () in my sessionID with character entities so we get a page cannot be found error.

Is there anyway to trap this on my end and replace them back with proper brackets?