This appears to do what you are asking for:

=SUM(INDIRECT("a" & ROW(A1) & ":a" & $C$1))

"Jeff" wrote:

Hi,

I have a formula that sums the range

Cell B1 = Sum(A1:$A$100)
and this is copied down to cell B100,
so Cell B33 = Sum(A33:$A$100)

But I want the sum range to change, based on the value in cell C1.

If C1 = 100, then the sum range will = Sum(A1:$A$100),
Cell B33 = Sum(A33:$A$100)

If Cell C1 = 300, then the sum range will = Sum(A1:$A$300)
Cell B33 = Sum(A33:$A$300)

I tried using indirect but I could not figure it out.

Thanks for your help