Calculate tax in BADI while editing PO

Hello

We have developed BADI ME_PROCESS_PO_CUST

In POST method i want to Calculate Item wise Tax value based on PO edited Values

I am using  CALCULATE_TAX_ITEM to calculate tax against item.

I used all the FMs mentioned in wiki.sap Docs

While PO creating time values are coming correctly.. but PO Editing Time values are coming completely wrong.

Same code used for Creating and Editing time.. And values also similar.

If i use the FM from SE37 with same vales which i am passing to  I_TAXCOM in BADI too.. from SE37 it's giving correct vales but in BADI vales into  T_XKOMV are differing

Any alternative to calculate PO Tax other than this FM to calculate Tax values Dynamically while editing PO.

Can I use this FM in BADIs while editing PO?

Thank You in Advance