Is it possible to run apps concurrently in different "Users" on Mac Pro in latest OSX?

Question

I wish to continuously monitor different folders in Dropbox for "input transactions" destined for my
applications on my Mac Pro, where each Dropbox folder represents different input types from different
sources. It would speed up the process significantly if my monitor program could run concurrently from
each of several defined "Users" on my Mac Pro with OSX.

Answer 1

Thank you for your response. Let me give you some more facts on my situation.
My monitor, running on a Mac Pro, reads folders owned by my clients, where the folders are shared
thru Dropbox with my service. So, yes, my monitor is "reading" different Dropbox member's folders looking for
"input" files to my service. My monitor is programmed (with a list) of the various clients' folders
names in which to search. Obviously, there is some number of clients (and folders) where the monitor
begins to take several seconds (too long) to scan and service, merely due to the sheer number of folders being
scanned. So, if I could create a second User on the Mac Pro, and run another (copy) of the monitor
programmed with another unique list of folders NOT being serviced by the monitor in the first
User, and (here's the problem) both monitors were running CONCURRENTLY, then the total number of
folders (and clients) being serviced could possibly almost double. Then, I could add a third User, then
a fourth, etc. to handle even more clients and folders.
The giant problem here is, each separate User does NOT run concurrently with the others, certainly where
all are logged in and "running". Actually, it appears OSX only executes programs within ONE user at a
time: the one in focus at the time. It so happens that OSX multitasks within that one User the differently-named
programs quite well; but OSX does not (continue to) execute anything in other Users, until another
User is manually switched to. Therefore, in my case, I can only run one monitor in one User at a time, thus ruining any benefit I might otherwise achieve IF OSX ran programs concurrently in multiple Users, another form of multitasking that apparently OSX is not designed to do. My monitors run with Excel VBA, which becomes the name of that program within
one User, so I am limited to running only 1 monitor per User. (Groups don't help.). On the other hand, It might help a little if
my monitor somehow could switch between OSX Users programmatically, rather than manually...I do not want
to sit at my Mac Pro constantly and manually fast-switching between Users to even attempt to solve my problem. Rather, I want
the software to run concurrently 24/7 unattended to successfully provide the service promised to all.
So, because there are lots of brilliant folks that know a lot about MACs and OSX, certainly more than me, I
am wondering IF someone knows how to get OSX to multitask across more than one User at a time, which
would solve my dilemma?? Maybe it's just not possible, I don't know...
Also, would OSX Server edition maybe be better suited to solve my problem? I know nothing about the Server's capability.
I would also hate to have to run Windows on my Mac Pro to solve this. Would VMware/Fusion work here?
Thank you again for taking the time to help...