SAP transformation merge cells

Hello,

I create an excel file using transformation.

I need to merge cells without know exactly how many cells must be merged. I need to use a variable/parameter to determine this number.

The programme determines the number of cells merged and passes this number to the transformation:

w_nb_cell_merge = 9.

CALL TRANSFORMATION ztest

SOURCE w_nb_cell_merge

RESULT XML  lw_string.

Transformation Ztest:

              <Cell ss:MergeAcross= "w_nb_cell_merge" ss:MergeDown="1" ss:StyleID="s66">
              <Data ss:Type="String">CORE FUNCTIONS</Data>
               </Cell>

Do you know how can i do that.

Thanks,

Patrice.