How to get Module A “after click save button” event to Module B

I am using amasty store locator, in that module we can create an attribute, i have two attributes, attribute 1 is filled by manual, another attribute 2 is filled by automatically. In module A click the save button after entered attriubute 1 pass that attribute 1 value to Module B doing some API thing after that i am getting one value and save it into Module A attribute 2. Here Module A and Module B handshake for sharing the details. What is the way to achieve this?