The "sumif" formula will calculate a range for you.
Example:
SUM(IF('Report Data'!$D$3:$D$3000="r17",'Report Data'!$P$3:$P$3000,0))
In the above formula, all values in the "P" column in my "Report Data"
worksheet will be added together if they there is a corresponding value in
the "D" column
Or if you have no qualifying criteria, just using the auto sum and then
highlighting all the cells you want to calculate.
Hope this helps.