As Mike elaborated, the field "Priority" has to do with how Project does
resource leveling. When you use resource leveling (which I don't think
you are nor do I think you should), Project will delay tasks with lower
priority, e.g. putting priority on tasks with higher priority. That's all.
Project does not schedule. Project can be immensely helpful to you in
developing a schedule. It is you who does the schedule. I think it
best that you not try to learn how to use Project from reading the
threads here. Best if you read the Project Guide (in Project), Project
Help, buy a good book on Project, or best--take a class. Also Mike has
his project tutorials available free. See the link he provided in his
reply to you:
http://tinyurl.com/2xbhc.
The resource will only have spare time, I think, if a) they have
finished early on a task that has been scheduled, or b) you have not
fully scheduled their time.
There may be fancy ways to model the situation that you are trying to
model; but I think that is over-kill. The best (and I think only) way
to plan for this ability for the resource to assist with another is to
simply get them to decide to do it. If they have time, and if there is
nothing else in the plan that they are schedule to do *now*, then use
the time *now* to help with another task. You can still record that the
person spent time on that task they help on, if you like.
My point, though, is that Project will not detect when someone has
"spare" time and then because of that spare time reschedule their work.
You do that. Or the person does it and then tells you they have done
it. Project is pretty sophisticated in this calculations; but it is not
"intelligent". It does not decide.
--rms
www.rmschneider.com