While browsing through the "additional widgets" on the widget website, I find they have one for depth of field, if any Mac users are interested...You have to have the Tiger OS. Click on the dashboard icon, then bring up the widget bar. When you do, you should see a click-tab called, "Additional widgets" on the right side of the screen. When you click on that, you go out to the apple web page for widgets. They have several categories -- many categories -- but it's under calculations. Click on calculations and then scan down the list to depth of field calculator.
JC