Yes This can Possible. You should do following Steps in Sales Entry 1. Purchase Voucher type Name Selection 2. Each Item you should give option to select Purchase Ledger 3. If the same values no issue, if rate different than, you should give option to input Purchase Rate also On Sales Form Accept, Add a Function and Create a Purchase Voucher That's It..! Don't forget, If you alter Sales entry, there is no possible to alter already created Purchase Entry.
