Create Canonical URL's

Hi there.

I see that the Metatag module has the ability to add a 'global' method to the canonical field, using a token. Is it at all possible to be able to create the canonical url from within admin area for a specific node? The nodewords module allowed this functionality in D6, but this updated version for D7 does not seem too?

As an example: a site has two events set for seperate dates, though the content on both of these pages is identical (aside from the date information). I wish to use the url from the initial event, for the second, duplicate, event. If this is possible using a token then I would greatly appreciate any help with how this token may look. I have been unable to locate any information that speaks to this.

AJ