Hi Ashlee , this is for sure do-able. I have an example of this I just did for a client, however instead of using Combo Box selectors, I'm using the button component. Which has an advantage because the button component property for Button Type is 'Select Member' which I believe is more user friendly than a combo box if there are many, many selection options.
Button 1 - needs a dashboard extender rule function Server Task to apply the parameter selection to the next component. It would look like this:
The key line of code there is the ModifiedCustomSubstVars action on the Selection Changed Task Result.
Button 2 - That parameter selection in the ModifiedCustomSubstVars I'm using as the Bound Parameter is button 2.
Lastly, the button actions need a User Interface Action of Refresh the embedded dashboard that contains the component selectors (Button or Combo Box). Otherwise you won't see the update immediately in your UI.
Hope this helps,
