I'm writing a formula that will be repeated down column B of a table. The formula sums 55 values in column A of data, and finds the percentage of that sum the current parallel cell in column A represents.

There are 45,000 rows in the table.

The formulas in column B need to sum the first 55 cells of column A, and then starting in cell B56, the formula for the next 55 rows needs to sum cells A56 through A111, and then update to sum the next 55 values in the column when it reaches cell B112, and continue to update to reflect the sum of the next 55 rows until the last row.

Below are the first three formulae, from cells B2, B3, and B4:
=A2/(SUM($A$2:$A$56))
=A3/(SUM($A$2:$A$56))
=A4/(SUM($A$2:$A$56))

Below is the formula in cell B56:
=A57/(SUM($A$57:$A$111))

I'd like to Use Edit > Fill > Down to enter all the formulae into the 45,000 rows of data, but because the sum function has to be identical for 55 rows, and then be updated to a new range for the next 55 rows, I can't.

Is there a way to enter the correct, changing formula in all the cells of column B without copying and pasting 55 cells at a time?

Thanks for any help you can offer!

- LCamille