Redwood - Default a DFF from values of another DFF's on the Job Requisition AutoComplete Rule

Summary:

We are trying to fetch data into a DFF by concatinating the Values of two other DFF's, all these DFF's are lying in Details section in create Job Requisition flow

Content (please ensure you mask any confidential information):

Customer uses only Job Requisition Template to create Requisitions. while creating the job requisition, the DFF -'A' must check that the User enters 'Yes' in a DFF 'B', if this is choosen 'Yes' then DFF 'A' concatinates the Values in another 2 DFF's 'C' and 'D' and shows it after the Requisition is submitted.

Is this possible with VBS rules? if not when we will be equipped to achieve this logic through VBS?