Using variables (or something similar) in multiple expressions

what you are looking for is called Measure Branching, and this is a technique that Sam uses throughout his training videos.
Below are a few forum posts that should help:

https://forum.enterprisedna.co/t/measure-branching/5962?u=heather
https://forum.enterprisedna.co/t/this-is-where-the-measure-branching-methodology-really-shines/4944?u=heather