I work with an older gentleman who needs to update his contacts regularly. Is there a way that I could just send him a properly formatted file that he could open as an attachment on his blackberry that would update his contacts?

Here might be one way to do it:

If you maintain the user's contacts on another system, say Outlook on a computer, or on another BlackBerry, you can make changes to the contact information on your system and then send the updated contact as a vcard attachment to the user. When the user clicks on the attachment he will have the option to Update Contact, which will change the contact info on his BlackBerry.

And if you add a new contact to your system and send as a vcard to the user, he will be able to save on his BlackBerry.

The above would allow you to send updates on the fly, so to speak. An alternative would be to just periodically sync the user's BlackBerry with Outlook on a computer you maintain.
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You might also set his contacts to sync to GMail. You could manage them via web browser as long as you can log into that Google account. His contacts would sync in near real time with the Google cloud. You could add contacts via browser to his GMail contacts and they'd to directly to his handheld. Additionally, as he adds contacts to the BlackBerry they go straight to GMail contacts.

That sounds like a nice idea for an application.