Hi, the most simple thing is to use a program called "Swap screen" (Read about it here:
http://dualmonitortool.sourceforge.net/swapscreen.html )
Here is a direct download as well(Also on their website):http://sourceforge.net/projects/dualmonitortool/files/latest/download
To use the Cursor lock function open Swap Screen and go to the Cursor tab, Locate the 3rd "Change..." button and then select your wanted key combination (I Recommend doing Ctrl + Shift + any key so that you don't accidentally activate it, but you can set whatever you want.). Now go to the "General" tab and make sure "Start with Windows" is checked so you don't have to manually open the program every time. There is a lot of outer things you can do with the program as well, see if you find something you like.