"Custom" candidate field

Content

I have a candidate standard field called "Requisitions" that is listed with a type of Custom.  We recently added this field to our Submit Employee Referral page.  But, this field returns a separate window listing all requisitions, regardless of posting status, which is allowing employees to submit candidates and associate them with requisitions that are either not open or not posted.

I don't have the ability to edit this field so I'm thinking that maybe Taleo created this for us?  I would like to leave this field alone but add a similar field that opens a separate window listing all open,