Grand Total in Excel Template

Hello,

I have a data model with multiple queries. The Excel Template that I built is structured to show one Tab for each group in the data model.

Now the requirement came in that for some fields, they want the column to total at the end.

I followed directions from that documentation and created a field and in the XDO_METADATA tab, changed the formula as follows:

<?sum(.//COLUMN1)?>

Now, it so happens that the field COLUMN1 exists in two groups and this results in the summary including both group's data thus giving incorrect results.

Is there a special syntax that can be used to only sum COLUMN1 for say G1 group?