Redmine

I would like to write a plugin which provides a custom field for "google documents". The idea is to let the user search in a popup or via autocompletion in his/her google docs, and create a link to this document from within a ticket.

I'm already finished with the javascript prototype to collect the google docs through the google data api, but i'm not sure how to make the redmine plugin alter the way how the customfield is edited.

Specifically i would need to load a custom javascript when a issue is edited which has the "gooogle doc" custom field.

Any hint how i could implement this?

thanks!