Hello, I'm looking at my dataset on our platform users and am trying to make a domo card that shows the "quick ratio" for each month, which is (New + Reactivated) / Churn. 

My dataset has the following columns:  Month / Active Users / New Users / Reactivated Users

For example for Month 2, Churn is found by: 

Month 1 Active Users + Month 2 New + Month 2 Reactivated - Month 2 Active Users

or the same:

-1 * (Month 2 Active users - Month 2 New - Month 2 Reactivated - Month 1 Active Users)

How can I make a beast mode to reflect the quick ratio? I tried what's below but am just getting a blank result, even though it says the formula is ok. 

case when `month` = 2 then -1*(`activeusers` - `New + Reactivated Users` - (case when `month` = 1 then `activeusers` end)) end

...I'd then continue the when statements for each month going onward... when month = 3 then ....

Thanks in advance!