Perhaps it should not need to be pointed out yet again, but flat
assertions of the sort that include the words "can" or "can't" -- and
their close cousins, "must" and "must not" -- tend to be dangerous to the
credibility of the person making such assertions because they are so often
wrong, and so easily refuted. Consider the instant case.
One of the inherent problems with developing in Access is that it is
INDEED very possible for two (or more) people to make two (or more)
changes to the same mdb at the same time. And that is a potential problem
for which any competent development team must account in its development
protocols.
In fact, one of the SOLUTIONS to this potential problem lies precisely in
creating a development protocol through which only one person has
authority to implement changes to a particular object in a "master"copy of
an mdb at any given time.
But then, wouldn't that be a desirale approach in any other development
environment, as well?
1. Only 1 person can make 1 change at a time with Jet.
If you just lost the training wheels and moved to Access Data
Projects, then you could hire multiple developers.