Send email notification to added employees when a record is added to a multiselect-lookup field

Hello,

I'm using Zoho Creator to keep tracks of who's responsible for each Function in the company.

Here's an example of a "Function" record:

Function name = Invoicing

Main owner(s) = John Doe

Substitute owner(s) = Amanda Lear, David Bowie

Where:

Function name: is a one-line field belonging to the record
Main owner(s): is a Multi-select Lookup field taking data from the "Employee" report
Substitute owner(s): is also a Multi-select Lookup field taking data from the "Employee" report

What I'd like to do is to notify the specific Employee via email when he/she gets added/removed from a function.

I was planning to do that by creating a Workflow on Record creation/Editing which will execute a Sendmail Deluge Script.

My initial idea was to save the values contained in the Main owner(s) and Substitute owner(s) fields in a couple of variables when opening the record, so I can match the differences when the record is save and send the e-mail only to the added/removed owner(s).

Anyway, seems like there's no way to save variables when opening a record.

Any hint?

Thank you