New attribute to be added only if there is no such attribute

[j.balasubramaniyam]

Please reply for my previous thread. 

https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/add-attribute-if-not-exist-in-a-part...

[john.uhden]

I think the easiest way would be to open the block definition with the BEDIT command and then use the ATTDEF command to create the attribute, then BCLOSE and save your changes.  Of course that will take effect in only your active drawing so you may want to WBLOCK the new definition.