i have a list of account numbers and transactions as follows:

48700 25
48705 33
48737 6
48766 15
48772 84
48792 52

i want to show count/sum subtotals (rollup) for the sub-series groupings where the last two digits are <= 49 and >49, as such:

48700 25
48705 33
48737 6
Series Count = 3, Sum = 64
48766 15
48772 84
48792 52
Series Count = 3, Sum = 151

i can't seem to get the group by to recognize the column alias i use for the account # last-two-digit substring so i can then use the rollup to give me the subtotals...how do i do this?

thanks so much in advance.