Hi Kapil:
Please refer to a previous post on the same topic:
http://forums.ni.com/ni/board/message?board.id=140&message.id=7758#M7758
Although this is for C++, the basic functionality should be the same. Since OUTPDATA is from a specific instrument driver, your best bet will be comparing it to the instrument drivers mentioned in the previous post.
Thank you,
Emilie S.
National Instruments
Applications Engineer