I do something similar but slightly different.
I've set up a seperate email address altogether and auto BCC all sent mail to that address. outlook in turn marks those messages read and moves them to my sent items automaticaly. Therefore I have a complete "sent" box in my outlook and I don't see sent emails in my inbox- ever.
My email address is
My auto BCC is "firstname.lastname@example.org"
Outlook takes any emails that come through the blackberry-sent account and automatically tags them as sent messages and puts them in my sent mail folder on my computer.
Works like a charm! And I love how transparent it is.