the value of reference field in the transaction cannot be extract into Gl journal line description i

Dear experts,

Currently, we have a requirement that we want get the reference of AR invoice into the GL journal lines after creating accounting. and in the "Source" field of "Journal Entry Description" screen,  i  don't find fields populated for the reference of AR invoice, then i try to populate it as "Application Reference Number", but it failed after i do the validtion in the "Application Accounting Definitons" form.the error information in the request is as below:

-------------------------------------------------------------------------------------------------------------------

The following journal entry descriptions assigned to the Error

  journal lines definition use sources in their details that

  have not been assigned to the event class. Please remove