what kind of change needs to be done with the database?
there are probally a few ways to go about this.
this is the first thing i could think of:
if you are just adding additional tables and fields you can do this
with tabledefs.
looks up createfield tabledef in this news group. you should find alot
of information and examples on it.
write a function in vba that changes the database.
create a new macro that calls that function and than quits ms access.
than you can create a .bat file that calls the macrao:
(ie "c:/programfiles/office/msaccess.exe" "c:/databasefix.mdb" x/
"macro_name")

burn the files to a cd and have the client run the .bat file, and all
of the changes should be made while not touching the current data.

Probably you need to write code in your VB front end to modify the JET
db. You can test it a million times until you are sure it doesn't mess
with the data. Then you can distribute it. You may need to write code
to check and see if the changes have been made so that they are not
done twice.

At the risk of incurring the wrath of the cdma thought police I'll point
you to my free tool (http://home.gci.net/~mike-noel/CompareEM.htm) that
is intended to do exactly what you are asking about.