Excel 2007 is a widely used, highly compatible spread sheet application. There are many tools in the software including the ability to undo actions, a tool found in many Office products.
To do this look for a arrow icon along the top toolbar. Next to it you will see the Office logo, a save icon and the redo button.
If you click this you will start the undo action. If there is no such a button, it means you need to add it into your quick access toolbar.
Click the rightmost arrow in the quick access toolbar, and choose the Undo item, then you will successfully add it into the quick access toolbar. To remove it from quick access toolbar, just uncheck the box in front of it.
It’s important to remember you use Undo, it “undoes” your actions in the exact reverse order that you applied them. Meaning that you can’t undo the third item in the list, without “undoing” the first two items as well.