Simple custom function for field validation

Simple custom function for field validation

Hi all,

I am new to Zoho CRM and Deluge.

I would like to set validation rule for the filed let's call it "Emails".
I would like to allow users to type in that field all characters that can appear in email addresses + comma, space is not allowed (in that field we are storing multiple email addresses and I want them to be separated by commas).

Thanks in advance!