Changing grouping on one one pivot table affects other pivots - no good

I have four pivot tables on four different sheets. when I use VBA to change the grouping on columns on one sheet, it also affects the other sheets. It also does this if I change grouping manually.

Example:
Three pivots are grouping columns by month (date columns).
On the fourth table (on a separate sheet), I use the VBA code:
With vSheetCtr.Range("B6") 'This points at the "JAN" title.
If .Value <> "" Then
.Group Start:=True, End:=True, _
Periods:=Array(False, False, False, False, False, True, False)
End If
End With
It works fine on that sheet, but it ALSO changes the grouping on two of the three other sheets. And it happens at the ".group" step.

Anyone? Thanks -