Unfortunately, the provided search results do not mention a specific "formula" for churn rate in Flex Workspace. However, I can suggest that you may be looking for a formula related to churn rate calculation.

In general, churn rate is calculated as the number of customers who stop doing business with a company over a given period of time, divided by the total number of customers at the beginning of that period.

If you're looking for a specific formula or tool to calculate churn rate in Flex Workspace, I recommend checking out the documentation and resources provided by Adobe Flex or other relevant sources.