Calculating Cells Used Based On Another Cells Data

I have a bit of an odd issue I need to solve. I use an Excel spreadsheet to track daily income for the store over a months' period. I have each day set to give me a rough estimate of profitability for that day. I also want to create a cell that tells me how much we've made so far, based on the number of business days so far in the current month. For example:

Day 1, $1500, $800 in expenses (monthly expenses averaged over the month, plus labor costs for the day), so a total of $700 profit.

Day 2, $1700, $749 in expenses (same as before), so a total of $951 profit.

The formula I'm using to calculate that isn't an issue, but I have the same formula for every single day, and each day has it's own cell with the estimated profitability for that particular day. In two other cells, I put the total number of business days in that month (in this case, 26), and in another cell I put the current number of business days we've had this month (in this case, 4), which is used partially to calculate the other cells. I want to use them to create another cell to contain the estimated profitability based solely on the number of business days out of the month we've had.

So E3 through E33 contain the individual days, I want to calculate - since we've only had 4 business days - what E3 through E7 would total. When I change it to 5 business days, i want it to calculate E3 through E8. So if we've had 4 business days, it only calculates the totals from the first 4 cells, if 5 business days, then the first 5 cells, etc, etc.

I can sort of picture it in my head, but I can't seem to find the necessary equation for it. It may require a macro, but I'd rather use a formula if possible. I'm not a big fan of macros.