Set value of custom field via link URL or form data?

Hi,

I have a somewhat complicated set of custom post types in WordPress 3.4, in which one of the type (Course Sections”) is really a kind of child of another type (“Courses”). Using manage_post_columns and manage_custom_column_content I now have a way to display existing sections of a course in the main edit page (that’s cool!). I also have a link in that column, “Add New Section”, which sends the user to a course section creation page. What I’d like to do is to prepopulate some of the custom fields in the new “section” with data from the parent “course”. Is it possible to do this by adding parameters to the URL, or somehow manipulating the $_GET or $_POST object from a simple (probably one-button) form?

I’ve been googling around but haven’t found anything that seems to tell me the secret.

Thank you!
Matt

ps, I can provide screenshots and things, though not links since all of my changes are in the administrative backend.