If you have outlook 2010, you will notice, you have a contact folder called "suggested contacts". If you dont have, turn this feature on:
see here for a description: Turn ON or OFF Suggested Contacts feature in Microsoft Outlook 2010
now, on a Desktop where the user has an installed outlook profile,
open a browser, and login to your bes: https://ip.addr.of.bes/webdesktop/login
if you have a BES express the default url is: https://ip.addr.of.bes:3443/webdesktop/login
in the webdesktop, you now are able to add the suggested contacts folder as a contacts folder for the handheld. See enclosed screenshot.
This feature is something only the outlook client is doing, so, as long as outlook is not running, no contacts will be auto-added. But, try it out, its better then nothing (or, you have to get a secretary as knotryrope suggested).