This script will depress the scroll lock key twice, enabling and disabling scroll lock. Slight overkill, including any mouse movement, but it should not be noticeable. This will prevent the screen from locking for just about any Windows setup. Just right click and choose Run with PowerShell when you want to keep your screen from locking.
Better Than Caffeine Programs
There are a lot of Caffeine clones out there that fail to keep corporate desktops unlocked. This PowerShell script registers an actual scroll lock press. The light will actually flash on the keyboard.