You are asking the wrong people entirely. There is no such thing as "the universal remote code for NAD DVD". What you want to do is ask the manufacturer of your universal remote control. The code you enter for any particular piece of equipment is determined by the remote maker, and it has to be supported by their preprogrammed database. The actual code, and whether there even is one, will vary between different brands of remotes, and sometimes between different models in the same brand.
If it's not in the remote you are out of luck with that universal, unless it is one of the One-For-All or Radio Shack remotes (+ some RCA remotes made by OFA)with "JP1" capability, enabling you to upgrade it. See
www.hifi-remote.com for details; search the JP1 forums and file sections for an NAD DVD upgrade code set.