You can do it with one of RIM's signed API's (controlled API's)
http://www.blackberry.com/developers...lledAPIs.shtml
You would be most interested in:
net.rim.blackberry.api.mail
net.rim.blackberry.api.pim
You will be able to test it in the BlackBerry emulator in the BlackBerry SDK, but you will need this application to be signed by RIM (for security purposes) for public release;