If you have been using a multi monitor system for quite some time now then am pretty sure that this tool would interest you.
The tool is called MouseTrap as it traps the mouse pointer within a single screen out of the other screens you are using. It is a very simple tool which confines the mouse pointer to a single screen on multi monitor systems.
When this program is run, it traps the mouse pointer in the screen where the pointer is present already limiting the mouse to move in only one out of the other screens. Simply unzip the file anywhere, and run it when required. Once running, ALT+Z traps the mouse in the monitor where the pointer is currently located, ALT+X releases the pointer and ALT+C exits the application.
The tool doesn’t require any installation and can be run directly even from a USB stick. The tool is very small in size and can be downloaded free from the link below.