you start getting into Win32 APIs when your talking Shellex keys - they have to do with 32bit Registered ClassIDs and . These are found under the HKCR\ClassID / Interface / and TypeLib keys - to name the main ones.
I did a test by selecting 3 notepad files at once and right clicking (context menu) and using my "Open with Notepad" add-on to HKCR*\Shell\Notepad...3 different/separate files opened at the same time - they were not all combined into the same Notepad instance.
Then I viewed with Process Explorer (www.sysinternals.com) which shows you the DLL dependencies for any module. What does this all mean ? not sure, except to say you may need to call Nero through a RunDLL.exe or RunDLL32.exe call (which runs a dll as an app) - more later perhaps.
I'm surprised you can even get it to burn at all, the way you have been doing ...allow me to ask - does the BurningROM GUI interface Open up in front of you during the process ??? and will it show the steps - go through the usual motions ?? (likely quickly) that one would normally see when burning a compilation ?
My point is - if you can get it to burn 1 file - you can get it to burn multiples - I just don't know how just yet - but there should be a way through command line. I'm not at all familiar with Nero's command line , and need to look into it further. Forgive me - but perhaps over the next few days, I may get a bit curious and mess with it - just right now isn't the time for me.
It's an easy answer, when it comes to batchs and commands - but it takes someone who knows...IOW it's very hard to lookup - you have to try and extrapolate from simialr examples.
some places to start looking (I assume you've been to Ahead / Nero's website);
as far as CopyToDVD - reminds me of an Free App i just recently uninstalled called CopyURL...which was excellent for use with IE (but I don't use IE, and haven't for quite some time now)
a few more tries/guesses for the moment - off the top of my head;
"%1" (enclose %1 in quotes)
%1 () (add blank parentheses)
variations of above
newbie try - similar to the \command\printto extensions found in the reg
"%1" "%2" "%3" "%4"
there are many combos to try that just boggles my mind sometimes (I'm not a programmer at all) using various batch commands like FOR - IF - GOTO - CHOICE etc
-- but maybe in order to grab a "group" or "multiple" files at once takes the Win32 interface using DLLs like Advapi32.dll, Comctl32.dll, Explorer.exe, User.dll , etc etc - at this point it's all merely speculation on my part
Can you post alink to the available Nero Command line switches and their uses ??