I was wondering if anyone has, or can help me figure out how, to use Document Links in order to proceed through a process. 

I want to have the process send out an email from an email address of a user of Laserfiche. The recipient of the email looks over the information and document(s) linked in the email and replies in an email with their approval/comments.

The reply goes to this LF User that not snapshots or saves the document into Laserfiche and sets a Document Relationship between the email and the document(s) that were emailed.

Once this Relationship has been set, I want to trigger the rest of my workflow to complete.

I was thinking of using "repeat" and doing a search on a delay, but that will not satisfy a client/user who is impatient. 

The other idea was have the user set the document relationship, and then change a metadata field indicating this step was completed. At which point, I would perform a search for the related documents and if I found none, then it would change that metadata field back.

Any recommendations or advice for this idea would be greatly appreciated.