I have a datadump into Excel once a month and the number of rows changes
every month. In the datadump are a number of columns. What I am trying to do
is to sum the data in column I based on criteria in column C, which is easy
enough to do using SUMIFS, however what I would like to do is to be able to
set the start row and end row manually. Ie the user dumps the data into
Excel, looks for the row number where the data starts, and the same for
where it ends and then input these two number into a block that the SUMIFS
function would pick up.

So for instance, the data data starts in row 2 and ends in row 48 so the
arrays in the SUMIFS function would be C2:C48 and I2:I48. I would then input
into the Start cell "2" and the End cell "48". What function would I use and
what is the syntax?