MM_PUR_S4_PR_MODIFY_ITEM

Hi Expert,
Need help in order to determine transaction code or reference when executing extensibility BAdI in S4 Hana Cloud
Scenario:
In the Service Order apps user able to add item and released it, once released the apps will generate Purchase Requisition .
When we do tracing this will called above BAdI , from the BAdI we will trigger warning message after checking input on a field.
But we need to use the same BAdI when user edit the data using Purchasing Requisition apps and trigger error message on the same field after we do the checking.
In order to do this we need to differentiate the transaction or the source of apps so we can trigger the correct error message.