Forms :: Warn User If Forget To Click On Save Control

I have a simple application where a user clicks on the name of the person he wants to update from a drop down box.

The record is then retrieved and the fields are filled on the form.
The user will then enter a value in the # in household field.
The user is then required to click on the save button to write the record for this person.

I do not have strong users and they invariably forget to save the record and go on to the next person, resulting in the record not being updated.

I coded a message box as part of the save button which displays "person was successfully updated" and then instructed the user to make sure that they see this message before they go on to the next person. They still fail to update correctly.

My question:

Is there a way when the user selects a person from the drop down box and it is loaded on the form, to warn the user that they have NOT updated this person, before they go to the next person?

I don't know what else I can do with these users. They are all volunteers and elderly and the application is for a Food Pantry.