I did the same cca. 2001 to a fellow female coworker. She had a big Excel document that day and was under pressure to finish it from her boss (well, our boss). She went to toilet and that's all it took me to set it, then maximize back her Excel document. She unaware worked for next hour and then when she finished she called the boss, which was across the room on his desktop, to verify it. The fun part came when I asked for something from her desktop and she had to minimize Excel. She went red in the face and the entire office burst in laughter for next 5 minutes, the boss included. After that day she learned WIN+L.