Hello,
I'm not quite sure what you mean. If you'd like to download the latest National Instruments DNET driver, you can do so here: http://digital.ni.com/softlib.nsf/websearch/0B70A796817D9C9086256D420061A1C3?opendocument&node=132070_US
This will allow you to examine the VC++ API for DNET, even if you do not currently have an NI-DNET card. Also, check out the DNET programmer's manual at http://www.ni.com/pdf/manuals/370376a.pdf .
Hope this helps.
Scott B.
Applications Engineer
National Instruments