How do I use a driven dimension from another part file?  In Part A I have a series of three diameters each having a particular number of thru holes.  I am now designing Part B that needs to use these same three diameters and hole counts to create some dependant features.  This is easy to do in a multi-part file but I would prefer to keep these two parts as separate drawing files.

How can I reference these three diameters and circular pattern counts in the Part B file?  I am using SW 2013.