enable a disabled button

i have disabled a button after the first click, but I want the button to be re-enabled when there has been a change in the workbook, not just a range of cells but the whole workbooks. So when any chnage is made on the workbook, the button should be enabled, and yet after another click, it should be disabled an so on, i hope you get the gist. I know someone out there has the excel magic I need. Thanks in advance for your help.