[ActiveDir] User Display Question

[Gilbert, Daniel L Mr ANOSC/FCBS]

To All:   If this issue has been covered before please point me in the right direction.   I am attempting to change the default display of users in ADUC.   I did some research and found Q250455, which is titled "How to Change Display Names in Active Directory".  Followed this Q article and new users created now display as: lastname, firstname.   Now my question, how do I make this change retroactive?  Should all existing users display change to lastname, firstname or do I need to run another script to change their display as well?   Daniel L. Gilbert