I am dabbling in launching a Podcasting series:

http://www.earlystage.com/taff.htm

If you listen to the first 45 seconds of the interview with Ed
Meagher, you'll hear a message from the sponsor and then the interview
will start. This is one MP3 file where I used an MP3 editor to
manually add the sponsorship messages at the beginning and end of the
interview. I keep track of the interviews and sponsor messages in an
MS Access XP database. I have the base interview file without
sponsorship messages, and every so often I want to be able to select /
create a new sponsor message and regenerate a complete MP3 file (the
file that includes the sponsorship message and the interview) from
within a VB module in Access. I may also want to have more than one
sponsor message at the beginning or end of the interview.

Misc facts:

* The base MP3 files (sponsor messages and interviews) are saved using
a variable bitrate (to make them as small as possible)
* I am currently using Wavepad to manually merge the files together
* I am willing to use an OCX / ActiveX control to merge the MP3 files
together inside the VB module -or- I can merge them together using a
product that has a DOS command line interface.
* I need to be able to merge at least five MP3 files together into a single file.
* The solution needs to let me edit the ID3 tags in the new (merged)
MP3 file -or- needs default to the ID3 tag on the first MP3 file in
the files being merged.
* The solution needs to let me set the name of the new MP3 file.
* The solution needs to save the new MP3 file using a varible bitrate
(the same settings the source files use -or- using settings I provide
from within the VB module).
* I would prefer that the solution include a free trial download that
will allow me to try it out and make sure it works in my environment
before I have to pay for it.
* Something like MP3Wrap (http://mp3wrap.sourceforge.net/) comes close
to meeting my needs, but it adds "wrap" to the file name, and always
sets the ID3 tags to "MP3Wrap" - I need to be able to set the file
name and ID3 tags.

If mp3wrap can do all but name the file and set the ID3 tag properly,
it sounds like all you need is a program that can change the ID3 tag. 
Changing the filename is trivial and changing just the ID3 tag
shouldn't be too hard.

If you search for "ID3 tag editor" you can find several freeware tag
editors.  You could make a batch file that accepts parameters for two
source files, an ID3 tagname, and an output filename.  Your batch file
would call mp3wrap.exe, run the ID3 tag editor, and rename the file. 
All you have to do then is parse the full command in your VBA module
and call the batch file using the Shell command.

Yeah, I can use MP3Wrap to merge the files, a command line ID3 tag
editor, and then rename the file, but I don't want to challenge Rube
Goldberg's homogeny over bailing wire and spit devices. Stated
differently, I am hoping for a somewhat more elegant solution that
isn't dependant on multiple freeware / shareware pieces of software. I
have already implemented the aforementioned solution, but it offends
my sense of neatness and I figured it's worth $10.50 to have a cleaner
solution.

I appreciate your input.

Have you ever thought of modifying the source for mp3wrap?  The main C
file is only 423 lines of code.  You could probably make the changes
you need with an hour or two of tweaking or spend a couple days and
port the whole thing to VB/VBA.  I'm always a big proponent of "ain't
broke don't fix it" but when you want it done right, you got to do it
yourself :)  Good luck.

The mp3wrap code appears to use GNU libraries, and I don't have a PC
that is set up properly. I'm not sure how much work it would take to
port the code to VBA, but at a first pass it looks like at least a
couple of days work, maybe as much as a week (depending on the GNU
library situation). Cheap SOB that I am, I'm still hoping that
somewhere out there is an OCX / command line MP3 file editor that will
work.

http://www.gold-software.com/download8280.html

See if that's what you want. Looks to run about $15 dollars.