VBA Code To Sum Values Across Multiple Rows

I got the following code to sum values for columns from this post in the forums. It works perfectly

VB:

With xl.ActiveSheet.Range("A7").CurrentRegion
If .Cells(.Rows.Count, 1).value <> "Total" Then
With .Offset(.Rows.Count).Resize(1)
.Formula = "=SUM(R2C:R[-1]C)"
.Columns(1).value = "Total"
End With
End If
End With

However I would like to do the same for the rows of data in my sheet, with a "Totals" column added on to the first empty column to the right. To provide some background, my worksheet is very similar to a pivot table. So the actual data starts a few columns to the right from A, and it extends to the right for an unkown length. I am using xlToRight to set a variable 'a'.

I like this code because it doesn't Dim any new variables because this will have to be re used about 5 times in the context of a loop and I already have way too many variables going. But if I have to use them it is okay.

I tried modifying the above code with .FormulaR1C1 = "=SUM(RC[-11]:RC[-1])" to no avail.