SM9.4 - how to change the field this variable uses $ ???

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 "$" value to search between dates , along with "$". I believe this value is based upon the request table "".

I want to change the field "$" 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?