The truth is, if you are looking for a secure system, don't use MSAccess. I love it and I work a lot with it.
But unfortunately MSAccess is not secure by any means.
No matter how deep you go into looking for security, it can be broken by automation in the end.
I think MS realize this and that's the reason in the newer versions of MSAccess (since 2007) you don't see those "security" tools you had in previous versions.
I'm telling you this because from my point of view nothing is worst than thinking you have a "protected" database when you don't.
As far as I remember some people of utteraccess did a great job building a security system for MSAccess, but still it has the automation problem.
So, my advice is use the tools both Matlab and MSAccess offer you, but don't break your head too much trying to make a bullet-proof app in security terms.