I gather that it is not your daughter who actually uses the mouse, but rather someone else who sets up the application for her? Have you thought about some sort of mounting device for the mouse that would protect it from accidental movement? The velcro idea mentioned earlier could be good, but my first thought was a little bracket that would hold the mouse around its edges and leave the ball untouched (another thought, what about the optical mouses that are available?). I think I've seen such mouse 'hangers' marketed for holding the mouse on the side of a monitor.

No matter what you do though, I think that some small mouse ball movement is going to be inevitable given that your whole workstation is on wheels (would an optical mouse generate random 'movement' from ambient light fluctuations?). Perhaps a switch wired in-line in the mouse cable could be used to disable/enable it? I know in Win32 one can (usually) unplug/replug the mouse with no ill-effects, and you could perhaps wire a switch to cut key wires to simulate this.

Update: Another thought: I don't know if/how you could do this with Perl/Tk but in Delphi I've seen applications that simply don't allow the mouse pointer to leave a specified area. This isn't friendly to other applications and you have to provide a simple way out of your app, but maybe this is an option (aha, baku has this idea).

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I'd like to be able to assign to an luser