Cell's math with selected cells  

You may want to do some math only with selected cells in the active worksheet
Or you may wish to do the math with selected cells in all sheets of your choice.

The Cell's math with selected cells tool does it for you.
This simple example will show you how to do it:
1. Select all cells you want to use as input for you math operations (in this example, select only some cells in the active sheet.) Then click on the Cell's math with selected cells button. The following dialog will appear:



2. Select the mathematical operation you want to perform.

3. Now you can set the way results will be displayed: either as formulas or just as values, or maybe as a link to those cells (this latest option is available only if you choose one cell in each sheet)

4. Choose the destination cell for results (as shown in the figure above)

That would be it. As results were pasted as formulas, the result will look like this: