Absolutely, you can add data across multiple worksheets in Excel using the SUM function with a special reference technique called a 3D reference. Here's how:

Scenario: Imagine you have sales data for each quarter in separate worksheets named "Q1", "Q2", "Q3", and "Q4". You want to find the total sales for the entire year (sum across all quarters).

Steps:

1. Choose the cell for the total: Select the cell where you want the total sales figure to appear. This cell will likely be on a summary sheet separate from your data sheets.

2. Enter the SUM function: Begin typing `=SUM(` in the chosen cell.

3. Use 3D reference: Instead of referencing individual cell ranges, you'll use a 3D reference to encompass all your worksheets. Here's the syntax:

`=SUM(Sheet1:SheetName!cell_range)`

- Replace `Sheet1:SheetName` with the actual range of worksheets containing your data. You can specify the sheets by name separated by colons (":") or use wildcards like `Q1:Q*` to include all sheets starting with "Q".
- Replace `cell_range` with the specific cell range you want to sum across all sheets. For example, if your sales data is in cell B2 on each worksheet, you would use `B2`.

4. Complete the formula: So, if your data resides in cell B2 on worksheets Q1 to Q4, your complete formula would look like this:

`=SUM(Q1:Q4!B2)`

5. Press Enter: Hit Enter to execute the formula. Excel will automatically add the values in cell B2 from all worksheets "Q1" to "Q4" and display the total sales figure in your chosen cell.

Benefits of 3D Referencing:

- Dynamic Updates: If you add new data to your worksheets or include additional sheets within the specified range (e.g., Q5), the SUM formula will automatically update to reflect the changes, saving you time and effort.
- Conciseness: It keeps your formula compact and easier to manage compared to manually listing out each worksheet cell reference.

Additional Notes:

- You can use this technique with other functions like AVERAGE, COUNTIF, etc., as long as they can be applied across multiple ranges.
- Ensure your data in the referenced cells across worksheets is compatible for the function you're using (e.g., all numbers for SUM).

By using the SUM function with 3D references, you can efficiently add data across multiple worksheets in Excel, keeping your calculations streamlined and your data analysis accurate.