Hi JohnnyW,
Unfortunately this is not a stock feature, however it can be done with some customization. If you want to try and customize it yourself I would suggest copying the CRM_EditDocumentLink screen and reverse engineering the actions used to link other records such as an Activity. I would also look into the Document... buttons that link the active recordID such as on the Quickbooks_Invoice screen.
If you're interested in learning more about customization we have some webinars here near the bottom of the page. Alternatively, I could put you in touch with an in-house consultant or you could contact a Method Solution Providers. Hope this helps.
- Jason