You have a list of contracts and due dates for annual maintenance fees. You wish to determine when you have a contract due in the next 45 days and provide a note that warns you that the payment is due. Using the IF function.

To determine when you have a contract due in the next 45 days and provide a warning note, you can use the IF function in Excel.

1. Assuming you have the list of contracts in column A and the corresponding due dates in column B, with the first row being headers, you can start by creating the formula in column C (or any other column where you want to display the warning note).

2. In cell C2 (just below the header), enter the following formula:
```
=IF(B2-TODAY()<=45, "Payment due in 45 days", "")
```

3. This formula checks if the due date in cell B2 minus today's date (TODAY()) is less than or equal to 45. If it is, it will display the warning note "Payment due in 45 days", otherwise, it will display an empty string ("").

4. Copy the formula down to the rest of the cells in column C to apply it to all the contracts.

Now, the cells in column C will display the warning note "Payment due in 45 days" for any contracts that have a due date within the next 45 days. If a contract is not due within the next 45 days, the corresponding cell in column C will be empty.

Note: Make sure the dates in column B are formatted as actual dates in Excel for the formula to work correctly.