How do I delete a custom date (in addressbook) with applescript

Question

I can't figure out how to delete a custom date for a contact.  I've worked with addresses and emails, phone numbers, but this one eludes me.
I want the script to go through all my contacts and delete every custom date whose label is "Mail Received"
I've searched and found a few people who had problems deleting custom dates, but I can't find an answer...
Thanks,

Answer 1

Hi,
Delete a custom date  doesn't work,  it's a bug.
Setting the value of the custom date to "missing value" works here (Mac OS X 10.5.8), but this generates an error (error : AppleEvent handler failed), I use a try block
Try this script
tell application "Address Book"
     repeat with theseDates in (get custom dates of people whose its label = "Mail Received")
          repeat with thisDate in theseDates
               try
                    set value of thisDate to missing value
               end try
          end repeat
     end repeat
     save
end tell