Several people suggested solutions; what happened when you adjusted to relevant ranges and tried the formula?
HELP has information on Subtotal
Returns a subtotal in a list or database. It is generally easier to create a list with subtotals using the Subtotals command (Data menu). Once the subtotal list is created, you can modify it by editing the SUBTOTAL function.
Syntax
SUBTOTAL(function_num,ref1,ref2,…)
Function_num is the number 1 to 11 that specifies which function to use in calculating subtotals within a list.
Function_Num Function
1 AVERAGE
2 COUNT
3 COUNTA
4 MAX
5 MIN
6 PRODUCT
7 STDEV
8 STDEVP
9 SUM
10 VAR
11 VARP
Ref1, ref2, are 1 to 29 ranges or references for which you want the subtotal.