Outlook 2007 add-in question...

Got a client who wants to have an email message either signed or
encrypted based on business rules. Idea is to intercept/capture the
"send" button and pop-up a form with a couple of check boxes. The
check boxes have straight-forward descriptions of the kinds of things
that need to be signed and/or encrypted, but abstracts the words
"sign" and "encrypt" into the "business language" the user knows.
User selects appropriate checkboxes, and the email is signed and/or
encrypted accordingly.

Couple of snags.

1) Can't seem to "undo" the sign/encrypt button if the user clicked it
prior to clicking send. Therefore, I'd like to disable the buttons on
the new message form. Any ideas?

2) Cancelling the form (and I set cancel=true in the handler) doesn't
always seem to cancel the sending of the email. Anyone seen similar/
have a workaround?

Thanks.