CVI 7 (released a couple of weeks ago) is the first version to support 64 bit integers. Without that, you could build a wrapper in Visual C++ and take two 32 bit integers to create a 64 bit (or vice-versa).
You can see more CVI 7 info at http://sine.ni.com/apps/we/nioc.vp?cid=11104〈=US.
An on-line seminar this morning said you could also goto http://www.ni.com/info and enter info code wecvi703, but that code's not working yet. I'll post an update if I find a new info code.