As far as I know, the only APIs which support NI-CAN are listed in this KB.
<a href="http://digital.ni.com/public.nsf/websearch/E4F5362A494B99C686256F4D006205C6?OpenDocument" target="_blank">http://digital.ni.com/public.nsf/websearch/E4F5362A494B99C686256F4D006205C6?OpenDocument</a>
Also, this question has been brought up before in this forum.
<a href="http://forums.ni.com/ni/board/message?board.id=30&message.id=2761&requireLogin=False" target="_blank">http://forums.ni.com/ni/board/message?board.id=30&message.id=2761&requireLogin=False</a> <a href="http://forums.ni.com/ni/board/message?board.id=30&message.id=1967&requireLogin=False" target="_blank">http://forums.ni.com/ni/board/message?board.id=30&message.id=1967&requireLogin=False</a>