How do I add a Google Analytics conversion value field to the "transaction" event?

Question

Google

It is necessary in the field conversion value - "google_conversion_value" (or in some other field), write the value according to the following formula: google_conversion_value = price / 1.35. This field (event) should be triggered by the "transaction" event and displayed here:

I was assured that it is quite possible to do this, but I can not find any information about this. Can someone tell me?