SM9.4 - how to change the field this variable uses $rm.adv.open.start ???

I am trying to setup a search for "before" and "after" based upon a new data field in the "request" table. The out of box uses this "$rm.adv.open.start" value to search between dates , along with "$rm.adv.open.end". I believe this value is based upon the request table "submit.date".

I want to change the field "$rm.adv.open.start" is using , but I cant find where this is stored and where to change it. I looked in global lists and scripts. 

Can someone point me in the right direction?