I don't believe this is possible.
The dimensions for threads found in standard holes (those created using the hole tool) are stored in files buried in the load point folders. With the dimensionsretrievedfrom an external file, I'm guessing that is causing them to become read-only, restricting them from being used ina family table.
Check in ../text/hole for a bunch of *.hol files. Wordpad will open these files, but notepad has issues with them. Other text programs should have no problem, such as ultraedit, crimson, etc.