Use the variable calculated by the average value for a specific field in the strip

I have a variable that stores the calculated average for a specific field.

Can this variable be used in the title bar? When I try to do this, I just get null in the header, but the correct value in the column footer.

The only other possibility for this that I see is to pre-compute it in Java and pass it as an argument, but I try to avoid this.

I am using JasperReports and iReport in version 3.7.4.