Is it possible to catch ALT+TAB and do nothing

[Igor Korot <ikorot01 gmail com>]

 Hi, ALL,
Is it possible to catch the ALT+TAB when one particular window is
displayed and do nothing, i.e. not switch to a different window?

We have a program which displays a full sized window without the
title. Its role is to Lock screen" - user should not be able to do
anything until (s)he supplies password and hit the "Authenticate"
button.
problem is that t is possible to hit "ALT+TAB" and switch the focus to
the window below it (such as Terminal) and type something.

We also can't use the lock screen window because of some other issues.

So is it possible to catch ALT+TAB and do nothing for one specific window?

On the side note - is there a better list (with more traffic) where I
can post  question like this? Or this list is still good and
operational?

Thank you.