How to custom running totals with global variables

Hello,

I'm having a problem with my report, the problem is:

I have two months for each records in my "Saldo" field, 1 and 4, the "Saldo" for month 1 is null, but the "Saldo" for month 4 isn't.

I need to retrieve each value of "Saldo" according to my group.

What I'm trying to do is:

(Formula names in bold)

====================================== REPORT HEADER ===============================

@Start (this one is supposed to declare the variable)

WhilePrintingRecords;

numberVar saldoTipo2_1Quad;

@Increment (this is supposed to increment only if the month is 4)

WhilePrintingRecords;

numberVar saldoTipo2_1Quad;

if (IsNull({Resultado_Primário.Assunto: LRF\Relatório Principal\Dcl V03\Mes Referencia})) then saldoTipo2_1Quad

else

if ({Resultado_Primário.Assunto: LRF\Relatório Principal\Dcl V03\Mes Referencia} = 4) then saldoTipo2_1Quad := saldoTipo2_1Quad + {Resultado_Primário.Assunto: LRF\Relatório Principal\Dcl V03\Saldo}

else saldoTipo2_1Quad;

===================================== REPORT FOOTER =================================

@Reset (This one resets the variable to 0)

WhilePrintingRecords;

numberVar saldoTipo2_1Quad := 0;

//////////////////////////////

Or either I get non-sense values (A sum of all values for that group) or I get a 0 or the first group gets a 0 and the second comes with the value which was supposed to be in the first group.

Thanks in advance, I hope you can understand my problem.