Subtotals Cause Hang With Large Data

I have a worksheet that uses Excel 2003's automatic subtotalling feature witSelectihin one of my macros. It works fine on my sample data, but when I try to run it on the larger set of customer data it hangs.

Any suggestions? I've been up all night, maybe this is just something really dumb, but I don't know. I stepped thru the macros, and it is hanging when I press f8 for the line that inserts the subtotals.

According to the task manager it really is hung, not just slow. Waited over 2 hours.

The line of code where it is hanging is:
Selection.subtotal groupby:=3, function:=xlsum, totallist:=array(14, 15, 16, 17, 18, 19, 20, 21, 22), Replace:=true, Pagebreaks:=false, Summarybelowdata:=true

I am a total newbie, so if there is a painfully obvious reason for why this is happening, don't think I'll be upset if you point out how dumb I am. Speaking of dumb, if this issue is posted elsewhere I apologize, I searched for hours before asking, but I may have looked in the wrong place.