Nullify CXC item level discount

Summary

How can we nullify CXC discount if the price of item after applying CXC discount is greater than externalPrice.

Content

We have a requirement where we need to nullify CXC discount if the externalPrice coming from external system has a value lower than the CXC discounted price.

Currently we are using PRICING_SUCCESS_CB and making a call to external system.If the externalPrice() on the cartItem is less than the discounted Price from CXC,we want to nullify CXC discount  and apply externalPrice.But this is not working as expected,it stacks both CXC discount and external Price.