Hello,
The documentation for the .NET language interface can be found in the common .NET help system. Start >> Programs >> Microsoft VS .NET 2003 (2005?) >> Microsoft VS .NET Documentation. Look under the National Instruments.NI4882 branch.
Now, what you're trying to do is a little advanced but I think I can describe it to you. You've been opening devices so far, but for your group trigger you'll need to open a handle to just the GPIB board so that you can send the command to every instrument at once.
-Initialize a board class for your appropriate GPIB board (probably 0 unless you hav more than 1)
-Board.Trigger( addresslist )
-Close the board class. Generally you don't want to use both board and device classes at the same time because they can step on each other.
Hope this make sense. Check out the help for more information on Trigger(). Let me know if you have further questions.
Scott B.
GPIB Software
National Instruments