Setting ``userfield`` in CDR log

Here’s my issue. I want to set the userfield CDR field for all children of a dialplan. My issue is I think each time I jump to a new extension, I need to reset the userfield data again (but by that point I don’t have the data anymore).

Basic layout:

500,1,Dial(local/600&local/700)
600,1,Dial(sip/user1)
700,1,Dial(sip/user2)

I really want to be able to put under extension 500 something that sets the USERFIELD for the CDR log to be something like ‘helloWorld’. But when extension 500 calls Dial() with a local extension, it seems everything is new as far as the CDR information goes. Can I set a Varible and then retrieve it from the other extensions? Suggest a work around for me or a proper method.