The trick, if you can, is to place your monitor so that you can see over the top to the door and notice if anyone is approaching... I've been like that for some time, it's saved my backside a few times. Rather surrepitiously hit the [X] on the browser window, with a spreadsheet opened behind it... looks like you've been hard at it and the brownie points come your way!
Cheers,
until you comp freezes and you have the pics stuck on your screen :lol: