How do I add a variable range of columns depending on criteria
 

I have a pivottable of sales data for 2008 and 2009 with rows for customers
and columns of annual totals, subdivided into months. I can extract the 2008
monthly data for month 11 using getpivotdata, but what I also want to do is
sum months 1 to 11 to give me the 2008 year to date information. I could of
course, just filter month 11 out of the table, but then I won't have an
actual 12 month total for 2008. Any suggestions??