In simple terms, you can't
The CAD (or Secure Attention Sequence) cannot be trapped by any process other than MSGINA.
So from VB you can't....
If you are very brave you can attempt to re-write the GINA. You will need to do this in C++. However, conventional wisdom says that this is a very hard thing to do! It is also extremely likely to prove fatal to the operating system several (many) times during development.
My advice: Rethink why you need to trap CAD! thread222-571474 thread222-541509 offer some additional reading...
Take Care
Matt
If at first you don't succeed, skydiving is not for you.