Do any of you Inventor users out there use hole charts on a regular basis?

My issue is that when I rev. a part by adding extra holes it usually re-arranges all the callouts.....e.g. a hole originally called say G3 when first released becomes say V5 on a subsequent revision.
Each new revision is correct within itself but any older rev. notes referring to previously added holes are invalid and confusing.

Any clues how you stop the hole labels from re-assigning?

Cheers,

Alan