Why wouldn't this work on a checkbox fieldChanged event? (Client-side)

This is only saying if the field is disabled or not. It's not setting the property of the field. /app.netsuite.com/app/help/helpcenter.nl?fid=section_4794215939.html

yeah it's readonly <-- least I thought it was, reading the image it states you can set it. 🙄

I would disagree with the above. I have definitely disabled/enabled fields using this on a client script before

So, ends up I forgot my field is in a sublist ... so in short, my code in fact works. Sorry everyone

Oops, there was a confusion on my end as well. Sorry!