As Lori mentioned, PTC_WM_NAME is not accessible in Creo. The best you can do is create a customization from the Windchill "Name" to some other custom attribute (parameter). According to the documentation, the customization will not allow you to use PTC_WM_NAME though. All PTC_** parameter names are reserved.
There are plenty of requests from others begging for this functionality. It makes no sense that Catia, Creo Direct, and AutoCAD can all access this parameter in their respective workgroup managers, but PTC's flagship CAD product, Creo Parametric cannot.
If you have maintenance, you can view (and vote up) the related product idea here: http://communities.ptc.com/ideas/4068