Can a custom date field be updated with today's date when "Send" is clicked on in Zoho Invoice. Or could there be a validation rule that checks for the custom field for today's date when "Send" is clicked stopping the action from happening and displaying an alert.

Background:

We track ar partially based on when an invoice is sent. The sent date is not available in Zoho Flow or Zoho Analytics. To get around this we have a "Date Sent" field that is manually entered right before we send the invoice.