Trying to get value from subreport...but give null

[sick35]

Hello everyone!

I'm trying to perform a sum of five values returned from equal number of subreports. The subreports work fine in the master report (I can see their results)... But the problem is when getting values from them, ('Return Values'). I created one variable (integer data type) on each subreport that gives total of records from each subreport and want to make a sum of them on a variable :

new Integer(          $V{varDespachoARegional}.intValue() +

                                 $V{varDespachoAConsulado}.intValue() +

                                 $V{varRegionalARegional}.intValue() +

                                 $V{varRegionalADespacho}.intValue() +

                                 $V{varRegionalAConsulado}.intValue()    )

I set this formula in the 'Variable Expression' field of the variable, but it prints only a "null" as a result in the master report. Am I missing something, or is something wrong? Thanks for your help