How to stop message " There must be at least one name or distribution list in To,cc,"

Hi all :wave:
I m working in OUTLOOK and VB 6.0
I want to stop the message "There must be at least one name or distribution list in To,cc,Bcc Box". That appears when user forget entering all fields To,cc,Bcc in a mail .
I want to trap this event.
I want to do something after user Press send button but before sending that mail. I want to check all fields To,cc,bcc etc, if all blank then I want to show my custome message instead inbuild message.
Anyone knows about this..?