It is possible. I do have a relation to find underscorer in the asm_mbr_name parameter in my repeat region relations.
This relation works on Creo Parametric 2.0 M020, but not on M030, M040, M050, M060 because it is bugged there. It's supposed to be fixed in Creo Parametric 2.0 M070.
This same bug happened to be in some of the Wildfire 4 subversions, which goes about 7 years back, but it was propably resolved back then. I'd think it was resolved in the latest WF4 subversions which i guess is M220. It has just leaked in Creo 2.0 M030 somehow.
I do have WF4 M220 at work, but I can't even figure out how to add a model to a drawing there. It's just so different compared to Creo 2.0.
If you can build some dummy assembly with a dummy assembly drawing to test this issue then maybe I can help you out. It really shouldn't be that hard.