Prevent Inferrance of Megafunctions

The global assignment worked - but trying to assign this rule to a specific part of the design did not.

I found the collection of registers that I need to apply the rule to via the drop-down menu in the 'To' textbox. I filtered on 'Registers: pre-synthesis' and added the name this way.

The collection always has a question mark by it, and the tooltip says that the name is not recognized (which seems odd, because I got the name from the drop-down list).

I've uploaded an image of this to google docs for reference:

https://docs.google.com/open?id=0b4wyejzmihtnzmnkued6aevhrnc

Any ideas?

Thanks!