Custom Link to Mail Merge

I have the link working to get to the mail merge page, but does anyone know how to add something in the link so the document is already selected? Or is it possible to create a link that will generate the mail merge and automatically take me to the task page after the merge page?

/mail/mmchoose.jsp?id={!Opportunity.Id}&1={!Opportunity.Name}&retURL=%2F{!Opportunity.Id}