URL groups set up for url with variable

Hi,

please, how can I protect visitors (unregistered users) to visit a link like that: http://domain.com/?wpdmact=process&did=Mi5ob3RsaW5r, where "Mi5ob3RsaW5r" is variable.

The only Q is: What exactly should I set up in URL groups to make this work?

Thanks, Jurij