[oXygen-user] Find and replace with lowercase

Hello, everyone, I was trying to find and change some attribute values to lowercase in hundreds of xml files, using the Find and Replace feature of Oxygen, but without success. For example, there are many values reading like this (just example): <mediaobject> <imageobject> <imagedata fileref="../images/AbcdEfg.png" width=".81cm"/> </imageobject> </mediaobject> I succeeded in finding all of those values using regular expression but I don't know how to replace them with their lowercase versions. Have you ever succeeded in doing the same thing? Would you please share the way you did it? Or it is just impossible with Oxygen? Thanks, Yudong