adding together variables returned from multiple subreports

[hondaman900]

I have several subreports and I can return and display values from each subreport, but need to display a result that is the addition of the returned values in a single variable. My variable expression adding the individual variables is as follows:

$V{monetary_sub_sum}.add($V{personal_sub_sum}).add($V{invest_sub_sum}).add($V{real_sub_sum})[/code]

The problem is that this returns "null". No errors, just no result. Since the individual variables show the returned values and display them in the same band in my report as I want to show this cumulative value, I'm not sure where to go next to resolve this.

I'm using Jaspersoft Studio 6.6

Any suggestions?