I am trying to add the custom property “Finished Length” to a batch of files. Some files have the custom property already and some do not. Some of the files that have the custom property have a value for that custom property. I want to add “Finished Length” to all the parts that don’t already have it, but I don’t want to remove the value present in the files that already have “Finished Length”

The example below shows what I am trying to achieve. The top section is what we have currently have and the bottom section is what we are aiming for.

Part Name – Custom Property – Value

Part A – BLANK - BLANK

Part B – “Finished Length” - BLANK

Part C – “Finished Length” – 123

Part Name – Custom Property – Value

Part A – “Finished Length” - BLANK

Part B – “Finished Length” - BLANK

Part C – “Finished Length” – 123

I have found a couple of macros that do something similar but they all overwrite the existing values with a blank string. I know that if I use the Custom property tab builder and apply the form that I create to a part, it adds the custom property if it doesn’t exist but does not overwrite existing ones. I just need to do this on a mass scale. Hopefully I can replicate this functionality?