I am new to this flavor of StackExchange, so if this belongs elsewhere, please move it; I figured this would be the best place, though.

I am making an Excel Worksheet that simply stores basic financial data in 5 columns (Check Number, Date of Transaction, Description, Profit from Transaction, and Balance After Transaction) and indefinite rows. Each worksheet represents one month, and each Workbook represents a year. As I make or receive a payment, I store it as a new row, which, inherently, makes the number of rows per month indefinite. Each transaction's Balance cell is the sum of the Balance cell of the row above it and the Profit cell of its row. I want each month to start off with a special row (first one after column headers) that displays a summary of the last month's transactions. For instance, the Balance After Transaction cell would display the last row's balance, and the Profit from Transaction cell would display the overall profits of the month)

I know that if I knew every month had exactly 100 expenses, I could achieve this for March with the following formulas for profit and balance, respectively:

=February!E2 - February!E102
=February!E102

However, I do NOT know how many rows will be in each month's table, and I'd like to automate this as much as possible (for instance, if I find a missed or duplicated expense in January, I don't want to have to update all the formulas that point to the ending January balance). How can I have Excel automatically use the last entered value in a column, in any given Excel spreadsheet, in a formula?