Need help with Differential backup

I have been running BUE 2014 for a little over a year.  I use it to perform some Full and Diff tape backups.  It does a good job and I am satisified with it.

This issue is dealing with something totally different.  See question below.

My Issue:  I am trying to perform a "to disk" backup of data based on the archive bit being set.  I have data that is being backed up to this server from a remote server.  It is a simple 2nd copy exact routine that runs nightly.  Most of this data is never touched.  I have cleared the archive bit on all of this data.  The total data is about 800Gb.  From this point forward, when new files are copied or existing files are changed the archive bit will be set.  I want to do a "backup to disk" differential backup of this data using BUE 2014.  Trouble is I can't figure out how to do it because it wants to run a full backup when I try to configure the job.  I can't figure out how to tell it NOT to run the Full backup.  I only want to run the Differential backup using the "archive bit" as the backup method.

Can someone please tell me how I can do this? 

thanks, tom