Customization in Vantage 6.1

I'm not haveing any luck finding info so, thought I would post. I need to set a custom field to required, or perhaps just pop up a message when a user changes the needby date on the sales order detail line screen. I can get the new field on there and know I can hook code to run on every save, just unsure how to go about that.


This is for our Vantage 6.10 app.. I know how to do it in Epicor 9, that is the sad part!