Combining parameters in Looker Studio

I have created a Looker Studio section entitled “Australia & New Zealand”) with two separate pages in it (i.e. ‘Australia’ and ‘New Zealand’). I want to be able to combine the respective sales forecasts of both countries within the ‘Australia’ page only.
To do that, I’ve created an ‘Australia Sales Target’ parameter in one Looker Studio page and a ‘New Zealand Sales Target’ parameter in the other/second page (entitled “New Zealand”).
The problem is that I can’t seem to add together the inputs for the two respective parameters (in their respective pages). The formula is straight forward enough (UA + NZ) but I only get the ‘Australia Sales Target’ if I display the result in a scorecard chart in the Australia page. Likewise, I only get the ‘New Zealand Sales Target’ if I display the result in a scorecard chart in the New Zealand page. I get that the parameters are page-specific only … How do I get Looker Studio to combine them? :thinking: