Sub SelectEveryNthRow()
ColsSelection = Selection.Columns.Count
RowsSelection = Selection.Rows.Count
RowsBetween = 3
Diff = Selection.Row - 1
Selection.Resize(RowsSelection, 1).Select
Set FinalRange = Selection. _
Offset(RowsBetween - 1, 0).Resize(1, ColsSelection)
For Each xCell In Selection
If xCell.Row Mod RowsBetween = Diff Then
Set FinalRange = Application.Union _
(FinalRange, xCell.Resize(1, ColsSelection))
End If
Next xCell
FinalRange.Select
End Sub