Anybody knows how to setup an email notification if an agent updates or adds a line item on a Sales Order?

For example, original Sales Order contains SKU #1 but agent changes it to SKU #2, is there any way to send email notification that the line item SKU has changed?

Another example is when Sales Order contains SKU #1 but agent adds SKU #2.

The short of it is, we need to have an email notification if any line items gets updated or added in the Sales Order. Thanks in advance.