use http://ahkscript.org/download/ - just download, install and run - you will get the menu where you can chose to open a sample script.
Replace it's content with this
this will make CapsLock to send Shift+Ctrl sequence.
Now go to the the "control panel"->"region and language"->"keyboards and languages"->"change keyboards"->"advanced key settings"->"change key sequence between input languages"->"switch keyboard layout". Chose Shift+Ctrl there. It should work now!