How To Make Descriptive Flex Field To Prompt Based On Document Style In Buyer Work Center And Core P

Greetings,

     My requirement is to make DFFs which will appear in the DFF having the title "PO_HEADERS" based on PO Style. I know how to use the functionality of Reference Fields while configuring a DFF, but in my case the reference field will be Document Style. so i don't know what is the reference field name that to be added in Reference Fields of that DFF under References Button in Register form. The Document  "How To Make Descriptive Flex Field To Prompt Based On Document Type In Buyer Work Center And Core Purchasing (Doc ID 1126873.1)" is similar to my case but the difference that my reference field is Document Style .