List of modification on a supplier form by mail through a custom event

Hello,

I want to create a custom event with a custom action to send by mail information that have been modified on a supplier form :

In the body of the message i’ve done this : 

Supplier &NEW:SUPPLIER_ID &NEW:NAME has been modified by #PERSON_NAME#.

But now i don’t know how to list the modification that have been done.

Regards

Pierrick