Default Values received from a web services in a Document of record field

Summary

Default Values received from a web services in a Document of record field

Content

Customer is using an application where user fills a Reference number >> taking this as input , a web service should be invoked to auto populate the information received in other fields

We are looking to provide DOcument of Record as a workaround but as per our analysis invoking any web services to auto populate certain fields are not feasible. Any pointers please.

Use case: 
Document type defined named as Mobile Bill Adjustment >> there are 3 fields in this document type DFF as Reference Number, NID, Total Permissible amount. >> Once user enter a value in Reference Number field >> A Web service with parameter Reference number should be invoked to fetch NID & Total Permissible amount and default that information in other 2 fields.