Possible to create my own variables?

Hello all. I am wondering if what I am trying to achieve is even possible. What I want to do is, in a way, have a global constant variable. The variable is an integer, which equals 432000. What I want to be able to do is use this variable across my dashboard, so when I build queries I can use this constant to limit my data.

Here is a graphical representation of what I want to do.


What I want to do:

Is something like this even possible to do? Thanks for all of those who reply in advance.