Hi kitty,
I don't know of an NI App note, but there's a .doc in the directory containing the VB files for the OI.
Is there something specific you're after?
A great place to start (because it's common to all the OIs) is with the TestStand programmes manual (from the help menu item in TS sequence editor). There's a section in there on writing an application with the API, and familiarity with this should help you understand the VB OI.
Another good place to start is to disect the code behind the OI that's in the examples directory (
\examples\Operator Interfaces\simple VB).
There's no .doc with this example, but since it's quite cut down, it should make life easier to get an idea of the methodology used to interact with the TS Engine.
Hope that helps
S.
// it takes almost no time to rate an answer