How can I get a notification on a field?

On the line level we have a field called unexpected ship date. When it is updated I would like to have it notify the account rep. However the line field is not available in the saved search. Any ideas? The best Netsuite came up with is- There is a the possibility of using a Workflow to send the email when the line field that you are watching over has been changed. It may possible through a Sublist Action Group running on after record submit and adding a condition that it should only send when the line field value has been changed.

But I am not sure how to do that.