Cancel an endpoint workflow with a custom function

Hi,

I have endpoint A.
I have a custom function A which does some calculations and defines if endpoint A should be stopped prematurely.

Can I stop endpoint A by adding a 'Return' function (or any other function that allows stopping a running the workflow) into custom function A or I will have to add the 'Return' function to endpoint A necessarily?

I would prefer to have everything inside the custom function so that I can reuse it on other endpoints.

Thanks!