Webcam through TMG

[Sheridan]

We use TMG as our edge firewall and publish the website through it (web publishing rule with external IP)

 

I would like to add a webcam to the site and use the existing external ip (we have no more spares) and publish it as http://www.website.co.uk\webcam so that link goes direct to the webcam feed through TMG - is that possible? I've tried a few configurations but it always seems to go to the web server itself, which reports that \webcam doesn't exist (which is true!)