Add prefix to custom property macro

I'm trying to write a macro to add the prefix "1-0" to the custom property "ItemNumber".

I've been able to use #task to add prefix/suffix to configuration specific properties in the past, but it does not work for only custom properties.

I've attempted to use this reference macro, but it doesn't seem to do anything?

2017 SOLIDWORKS API Help - Add and Get Custom Properties Example (VBA)

SolidworksApi macros