Replace a query string variable value

Give this a shot:

when HTTP_REQUEST { 
   HTTP::uri [string map {"rbweb--dev%2egerbc%2erbcmtg%2ecom" "172%2e16%2e20%2e83"} [HTTP::uri]] 
 }

When you said it didn't work for values, what did you mean? I tested this out with a test URL of

http://myserver/foo/bar?TARGET=-SM-http%3a%2f%2frbweb--dev%2egerbc%2erbcmtg%2ecom%2fcar%2f

and it changed it and sent it to the backend server as

http://myserver/foo/bar?TARGET=-SM-http%3a%2f%2f172%2e16%2e20%2e83%2fcar%2f

Of course, if you need to expand this, you could put the relevant URL's in a class and do a lookup and then a replace based on a match in the class but you only specified that you had one url to change.

Hope this helps...

-Joe