Is it possible to dynamically change the value of a hidden control variable ?

[Jonathan Lowry]

Is it possible to dynamically change the value of a hidden control variable, specifically with other controls on the same dashboard?

My scenario, is that a lot of the templates for Analytics that utilize Project_ID and to change that across all of the different metrics on the Sprint Overview would take some time. I need to add an additional criteria that can narrow down the project/sprint even more - like the Board_ID. 

So, is it possible to use the dropdown for PROJECT_ID, where i can select a Project and it updates the Hidden Variable Control on the same dashboard with the Board_ID that I can then use with other charts on the dashboard?