Can't anyone help me?

How do I use the DBGrid's button property? The help that I have just says:
Typically, you enable the column button when you want to drop down a control (such as the built-in combo box, a bound list box, or even another DBGrid control) for editing or data entry. When the button in the current cell is clicked, the ButtonClick event will be fired. You can then write code to drop down the desired control from the cell.

It doesn't give me an example or anything else on how to do this. Can someone help with this?