Hey Craigr,
Couldn't you make it an attribute not visible unless using quick properties?
I have never messed with Attributes. - I will have to look into that.
Thanks
+1. Invisible attributes have long been a means of adding extra information to blocks, even before XDATA and Extension Dictionaries/XRrecords. One thing to watch out for are blocks with *only* invisible attributes - out of sight, out of mind. When users insert drawings wholesale and explode them, those "invisible" blocks come along for the ride as well. I've had drawings which have circulated for a couple of decades and ended up with tens of thousands of these things. ATTDISP command is my friend