Create a Vacation Rule based on 'FROM'

The existing workflow is

A -> B-> M

or

D-> E-> M

"M" is the Final approver.

"M" is going on Vacation. We would need to create a Vacation rule such that if the Journal Approval Notifications is from "B" then delegate it to "E" and if the Journal Approval Notifications is from "E" then delegate it to "B"

To Be:

A -> B-> E

D-> E-> B