1. On the Company sheet, select cell B2 and type an equal sign =

2. Go to the North sheet, select cell B2 and type a +

3. Repeat step 2 for the Mid and South sheet.
Result.

4. This is quite a lot of work. Instead of doing this, use the following 3D-reference: North:South!B2 as the argument for the SUM function.

5. If you add worksheets between North and South, this worksheet is automatically included in the formula in cell B2.
