Does anyone know how I can track when a user clicks on the 'Copy Previous' button at line level on a record i.e sales order - how to then populate a field value on that line only then?

I was just wrangling this a bit the other day - it seemed that in my case, the only event fired was a fieldChanged on the department field in the event of using the line level copy button.

hmm.. I'm also trying to do the reverse which is to blank out certain field values when 'Copy Previous' is selected which is frustrating