Hi Chris,
Welcome to the wonderful world of Access.Your questions/expressed
desires indicate that you are not yet familiar with Access under the
hood. Be warned, there is a longer and steeper learning curve in
Access than in the other MS Office applications.
There are several Access newsgroups and the most useful ones for
people learning the basics are: microsoft.public.access.gettingstarted
and microsoft.public.access.tablesdesign People who have mastered
Excel or who may have Access Step by Step may feel that those
newsgroups are beneath them. They aren't.
Tablesdesign is all about the organization of your data. That seems
so boring and uninteresting to people starting to learn Access.
However, if you stay with it you'll come to understand that the
characterization of the entities in play in your applaction (entities
are captured in TABLES) is crucial to creating a useful application.
If you already understand terms like "normalization" and know what
"third normal form" means without having to think about it then you
may not need to lurk tablesdesign. A couple of surprising facts you
should learn while lurking tablesdesign: Tables are cheap. You need
one table for each entity type. Don't try to cram several entities
together. Fields are expensive. Use as many fields as you need but
no more than that. When someone posts that they have a table of 60 or
100 fields it's wise to be suspicious of their data design. Get the
tables right and you can extend and enhance your application forever.
Get the tables wrong and your application soon becomes difficult or
impossible to enhance. Another thing is that data should never be
entered or massaged in tables directly by the user.
Gettingstarted expects that people posting questions there are humble
novices who are just venturing into the Access world. The people
answering posts tend to be appropriately considerate. That's actually
true of all of the Access newsgroups. Lurk the newsgroups to see what
others are posting and see if you can follow the initial problem and
what the responder(s) suggested to resolve the issue.
The first response to many posts will be something like: "You can't
do exactly what you asked, however, ...."
Limit yourself to one issue per thread. Once your initial issue is
resolved, don't piggyback a new issue onto the old one: :Oh, while
I've got you ..." Alsol, don't hijack someone else's thread. Start a
new thread for your new issues. Don't address your issue to a single
responder. some of us go for weeks at a time without checking in.
If you hope to make good progress in Access you'll be well advised to
visit your local bookstore. Browse several Access books and pick one
that seems to communicate to you. You'll be back again later for more
advanced stuff.

An incredibly valuable resource is
www.mvps.org/access It is filled with Access lore and continually
grows.
To your issues:
Name each table for the entity it represents. I doubt that "Main" or
"Master" is a good table name. Some candidate entity names: Person,
Site, Room, Job, Task, Order, Item, etc. Entities like Site or Color
are placed in regular tables but are treated specially as Lookup
Tables. You'll typically use a combobox to display all the values and
pick the one you want.
It seems that Task might be the thing your application is all about.
Your user interface (even if you're the only current user) should be
entirely via forms and reports. The forms and reports will be based
on queries. In time you may want to turn over the use of your
application to someone else. A good user interface will facilitate
that hand-off.
You won't need to CTRL-Click. The control you'll need in order to
associate just selected personnel with a given task is a Multi-Select
List Box that will list every person in tblPerson. Each person will
be individually selectable. In the OnClick event of the command
button you'll need to step through the index of the listbox and
concatenate the name of each selected person to the list in the textbo
x on your form...When you save your form, the field in the table will
be updated with the contents of the textbox.
HTH