Submit button for a form in Word

[pandaburgh]

I've built a form for my husband to send to his clients via email, using Word 2007.

It has a submit button which sends the completed form back to his email address automatically but I'm having trouble linking this to a thank you message when the submit button is pressed. At the moment, there's nothing to say that the submit button has worked, which isn't ideal as i found out when I sent it to a friend to test it and I ended up with about 40 copies of the same thing in my mailbox because he kept clicking the button thinking that it hadn't worked!

Does anyone know what I should do to get a thank you message to pop up? I haven't done anything like this before and Google hasn't been my friend in trying to find an answer, so I would really appreciate any help.