You would need a program that can intercept keystrokes and look for the CTRL+J combination. I'm not sure how, but if you could develop a program that would hook all keystrokes sent to Windows and filter them for CTRL+J, you could do it... this article may help:
If you want the form to open when someone presses this key sequence within your own program then that is rather simple. Using the keypreview property of your active form you can intercept keystrokes and have them tigger other code as needed.
If you are talking about intercepting keystrokes from the destop or other application then that is a bit more of an issue.