Report Builder - How to replace a value?

In the Report Build I want to replace a value with a better value. E.g. http://clmserver/users/unassigned with Unassigned or "no test result" with "Not Run". I got something working with:

IF ($VAL$ IN ("useruri"), "Unassigned", $VAL$)

I would like to have something like:

IF ($VAL$="useruri", "Unassigned")

But the http://clmserver/users/unassigned is not recognized. Have not tried similar approach of an empty string/no test run done yet.
(Global Configuration is enabled, so we use the "Delivery Stream").