CVI doesn't provide any functions for Binary Code Decimal (BCD) formatted numbers since it isn't part of the ANSI-C spec and isn't related to any of our libraries. You would have to do the conversions yourself, or find a C library somewhere that could do the conversion for you.
Here is a site that had an example of a BCD to double conversion function: http://dos.snippets.org/snip_lister.php?fname=BCDD.C
Best Regards,
Chris Matthews
National Instruments