You can't directly use the SUM function with checkboxes in Excel, but you can achieve the desired outcome by combining SUM with COUNTIF. Here's how:

Scenario:

Imagine you have a table with product names and prices in columns A and B, respectively. In column C, you have checkboxes for each product indicating if it's selected or not (TRUE for checked, FALSE for unchecked). You want to calculate the total price of only the selected products.

Steps:

1. Checkbox Setup: Make sure the checkboxes in column C are linked to actual cells (formatted as logical values, TRUE or FALSE). You can achieve this by inserting checkboxes and then formatting the linked cells as logical.
2. Formula with COUNTIF and SUM: In a separate cell (let's say D1), enter the following formula:

```excel
=SUM(B:B*COUNTIF(C:C,TRUE))
```

Explanation:

- `B:B`: This references the entire price column (B).
- `COUNTIF(C:C,TRUE)`: This part counts the number of TRUE values (checked boxes) in column C.
- `*`: The asterisk acts as multiplication.
- The formula essentially multiplies each price in column B by a 1 (from the corresponding TRUE value in C) if the checkbox is checked and by a 0 (from the corresponding FALSE value) if the checkbox is unchecked. Finally, it sums these products to get the total price of selected items.

Benefits:

- This approach dynamically updates the sum based on checkbox selections.
- It's relatively simple to understand and implement.

Drawbacks:

- It can be cumbersome for a large number of checkboxes.

Alternative (Advanced):

For a cleaner approach with many checkboxes, consider using SUMIFS:

```excel
=SUMIFS(B:B,C:C,TRUE)
```

- This formula directly checks for TRUE values in column C and sums the corresponding prices in column B.

Remember:

- Adjust the cell ranges (B:B, C:C) based on your actual data location.
- Copy the formula down if you want the total price for each product based on selection.

By using these methods, you can effectively calculate the sum based on checkbox selections in Excel.