My structure:
#header group1 with the client [background in silver] (with a function who clears the value of the variable-sum) 
    #header group2 with type of product (BR, CR,...) and a formula field to clean the variables in month formula// supressed
         #header group3 of a function who converts to date (only month) from text. //supressed
               #details with the numbers who I want to sum. // supressed

         #group3 footer with many formula fields that i make, for each month . (I will pot the code below) //supressed

   #group2 footer is wath you see with white background. In this section have a copy of the formula fields who stay in the group3 footer;

#group1 footer is where a placed the column sum formula field. [background in silver]

 

The month function:

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numbervar jan;
numbervar total_jan;
if GroupName ({@function_data}) = "01" then (jan:= {#RTZZB_QTD}; total_jan:=total_jan+janeiro;);
jan;

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{#RTZZB_QTD} is a Running total field who sum the numbers in group3 footer.

 

 

In the group1 footer has a formula who only shows the total_jan;

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numbervar total_jan;
{@01 jan}; // calls my month function
total_jan; //show the variable

 

Can you help me to make the Sum with columns?

Thanks