Hi,
The effective interest rate available in the transaction is specific for that purchase. Why do you want to change the effective interest rate in a bond purchase transaction after the sale has been concluded? The effective interest rate is essentially the YTM at the time of purchase and it is calculated based on the purchase price and other interest flows at the time of purchase. So after you conclude the purchase, irrespective of changes to interest rates, you cannot change the price/YTM at purchase.
However if you want to calculated YTM or effective interest rate after purchase, I think it can be done through MRA. From EH3 onwards, YTM is a key figure and can be calculated at portfolio level. In Portfolio Analyzer, you can calculate YTM at the ID level.
Regards,
Ravi