Monthly change in same deals' values

Jeeves Jay

Does anyone know how to get the change in value of all deals using Postman? I want the values at the end of a number of given months (since the value of deals change during negotiations). I've been playing around with it since morning, but since I'm not a developer it's hard to get my head around some concepts! I need to be able to present to our board the change in value of our pipeline (monthly) and take them through the reasons. Cheers!