URL Attachment to a URI

Our organization uses a browser based ticketing system (HP Quality Center) which utilizes its own custom URI to launch the application in a browser. We would like to link into this application by attaching URLs into a SmartSheet row. As an example, the URI looks like this:

tds://project.domain:port/qcbin/DefectsModule?EntityType=Bug&EntityID=12345

However, because Smartsheet seems to require that a URL attachment begins with "http" or "www" it is not accepting this URI. Am I doing something wrong??