A scripting language such as this is the way to go, IMHO.
I’ve never tried AutoIt; I use AutoHotKey for my scripting needs. It’s free and easy to learn, and can make standalone .EXE executables that don’t need the Autohotkey program loaded in order to run.
RedBarchetta, I recommend that you try the following steps (less than 5 minutes total). You can try it out at home first, then install the resulting .EXE file on your work computer tomorrow.
[ol]
[li]Download AutoHotkey from this page, and install it on your PC.[/li][li]Create a new text document using Notepad.[/li][li]Copy and paste the following code into the new text document:[/li]
StartWiggling:
SecondsDelay=1
Distance=1
MouseGetPos,OldMouseX,OldMouseY
MouseMove,OldMouseX+Distance,OldMouseY
MouseMove,OldMouseX,OldMouseY
sleep SecondsDelay*1000
goto StartWiggling
[li]Save the file as “WiggleMouse.ahk” (note the .ahk extension – it’s important!). You can save it to any directory that you want, or on the Desktop.[/li][li]To test the program, double-click on “WiggleMouse.ahk” in Windows Explorer (or on the Desktop icon if that’s the path you chose). You should see a new icon in your PC’s Task Tray – it’ll be a green square with a white “H” in it. Look at the mouse pointer carefully; it’ll wiggle one pixel to right – and rapidly back – once per second. The one-pixel wiggle is set by the “Distance” parameter in my above script, and the delay between wiggles is the “SecondsDelay” parameter. [I found that the one-pixel wiggle didn’t affect normal operation at all, since anything that you’re aiming at is bigger than one pixel wide, so you can leave the program running all the time at work.][/li][li]Kill the program by right-clicking on the “H” icon in the Task Tray and left-clicking “Exit”.[/li][li]Once you’ve seen it work, open up the “WiggleMouse.ahk” in Notepad (or right-click it and select “Edit Script”, which is the same thing). Change the “SecondsDelay” value in the second line from 1 to 240. Save the script file again. Now, when you run it, it’s wiggle the mouse every 4 minutes.[/li][li]If you want to save it as a stand-alone executable for use at work, click “Start -> Programs -> Autohotkey -> Convert .ahk to .exe”. Load the “Source (script file)” field by Browsing to the “WiggleMouse.ahk”, leave the other fields blank, and click the “>Convert<” button. You’ll get a “WiggleMouse.exe” in the same folder as the .ahk file.[/li][li]e-mail “WiggleMouse.exe” to yourself at work, download it, and try it out! If all is fine, install it in the “Startup” folder so it launches in the background on bootup. [/li][/ol]
The script took me about 2 minutes to write and test – much less than the time to write this post! 
It’ll be easy to modify if it doesn’t quite work the way you want it to (for instance, if your work’s XP patch doesn’t recognize a single-pixel wiggle, we can make the wiggle bigger). We could also try making an .EXE that takes command-line parameters. However, this quick-and-dirty version should work for you.
Don’t worry about having it running in the background all the time; on my PC it takes up 2.6MB of RAM when running, and consumes less than 1% of the CPU time (i.e. it reads as 0%) even running at one wiggle per second.
