Sorry to be so needy...first time doing this. Code seems fixed.
I have the button (EmailButton) with the Code behind it and the EmailSent (FieldID=57) Date time field.
I have created a notification as follows:
Notification When: a shipment is Modified and "Any of the following fields change with "EmailSent" checked.
I click the button and nothing seemed to happen.
EmailSent field still blank after clicking button.