I would offer good advice for this, except I use Mac's Numbers program, so the specifics won't really translate. But I can tell you what mine does if you want to figure out how to make Excel do it.

It's a multi-sheet spreadsheet. There's an income sheet, an expenses sheet, and a main budget sheet. That's the main stuff. The income and expenses sheets apply to the whole year. Each month has its own main budget sheet.

The budget sheet's main spreadsheet lists all my expected, budgeted monthly expenses. The first column names the expense, then there are columns for "Projected Cost", "Due Date", "Notes", a checkbox column for "Withdrawn?", a column for "Date of Payment", a column for "Actual Cost", a (technically intended as a hidden column, but I usually display it anyway) "money out" column, a "Cost Differential" column, and a "Paid on Credit Card" column. If Paid on Credit Card is checked, it zeroes the money out and cost differential columns (all of this is geared to tracking my bank balance, not cc balance).

The money out column populates from the "Actual Cost" value for fields with the "Withdrawn?" checkbox checked. The cost differential column does the same, but subtracts "Actual Cost" value from the "Projected Cost" value.

Attached at the bottom of that spreadsheet is a separate one-row, three-column spreadsheet of "Total Monthly Expenses". First column is Expense Budget, and that field is just a sum of the first spreadsheet's "Projected Cost" column of figures. The next column is "Other Expenses", which parses my expenses sheet for planned expenses labeled with that particular month. The third column/field is "Current Expenses Out" which sums the "money out" column of the first spreadsheet as well as sums expenses from the expenses spreadsheet (which is where I put planned one-time expenses and random debit card charges) for that month which are marked as paid.

On the main budget sheet for a particular month there is also a month-specific income sheet, which sums appropriate income from the separate income sheet (with formulas set up to account for disparity between projected and actual income). It displays expected income for the month as well as how much has actually currently been deposited.

There is also a Monthly Balance spreadsheet on this main budget sheet with one column and six rows. The first is "Previous Month's Balance", second is "Projected Income", third is "Projected Expenses", fourth is "Adjusted Cash Flow", fifth is "Projected End of Month Balance", sixth is "Available Balance".

Previous month's balance is pretty obvious. I manually input the ending balance from the previous month's sheet. Projected Income is pretty simple, it's just the sum from the Monthly Income spreadsheet, which itself is taken from the Paychecks and Other Income spreadsheets on the separate income sheet. Projected Expenses sums the Expense Budget field of the Total Monthly Expenses spreadsheet, the Other Expenses field of the TME spreadsheet, and also subtracts the Projected Cost value on the main spreadsheet for fields that have "Paid on CC" checked.

The "Adjusted Cash Flow" field is a formula that subtracts "Projected Expenses" from "Projected Income", adds the sum of the "Cost Differential" column from the main spreadsheet, and adds the sum of the "Income Differential" column from the Monthly Income spreadsheet.

"Projected End of Month Balance" is just "Previous Month's Balance" summed with "Adjusted Cash Flow". "Available Balance" is calculated by taking "Previous Month's Balance" and adding "Current Income In" (actually deposited) and subtracting "Current Expenses Out" (actually withdrawn).

I may have forgotten one or two specifics, and I left out a lot of the specifics of the ancillary sheets (expense and income sheets, expense type analysis charts, etc); it's pretty heavy with formulas all over. I'll try to edit any discrepancies or clarify any confusing bits once I'm at home and can actually reference the spreadsheet itself. Any errors you might deduce from my description are the fault of the description itself (things I forgot about how it calculates, etc.), the actual spreadsheet setup has proven entirely accurate for years now.

I love having a straight value for how much money is coming in or going out for a month ("Adjusted Cash Flow") and the "Projected End of Month Balance" is nice to get an idea for planning expenses for the following month, or knowing exactly how much I can spend at any given point. The "Available Balance" is even better than checking my balance online because there's no lag from checks or tips, etc.