Selected file/s in Windows Explorer (Shell)

Hi,
I develop a win-form application using VB.NET that uses a keyboard hook to
monitor when if the user types SHIFT+Z combination. What I would like to do
is to display a form when the user clicks this keys combination, but only if
the focus is on a file/s in the Windows Explorer. What I mean is that I when
the user select a file/s in the Windows Explorer and type the keys
combination (while the selected file/s are in focus), then the new form will
be displayed. Something similar to th contex-menu that is displayed by
clicking the right mouse key, but without the mouse...

Any input will be appreciated!
Thanks,
Tom.