Hello,
I use the

Range.Group Method
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When the Range object represents a single cell in a PivotTable field’s
data range, the Group method performs numeric or date-based grouping
in that field.

Namespace: Microsoft.Office.Interop.Excel
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after performing the groupment, I noticed that the groupment was in
columns, not in rows, as I expected. how can I group in rows? is there
a option to group rows or columns?