Get the total of two columns with number format using rtf template

Hi,

I have a report that contains two columns which is I want to get the total using the rtf. Now I tried the <?xdofx: to_number(VATABLE,'#,##0.00')+to_number(VAT_EXEMPT_SALES,'#,##0.00')?>

but it returned me a NaN. Then I tried the <?xdofx: to_number(VATABLE)+to_number(VAT_EXEMPT_SALES)?> but the result that I excpected is wrong. For example,

I have two columns,

Column1       Column21423             1555

Then I export the xml in the bi publisher using the microsoft word.

Now I want is to get the total of the two columns,

I tried the