ExcelBanter - Discrete "Normal" Curve Function?

Does anyone know off hand what the formula for a normal curve is, I'm trying
to work out what the y values are for each part in x

or, more explicitly

For a given integer total N, then given a two tailed normal (Gaussian), I
want to know the function values at M equally spaced points along the x axis

this isn't some kind of homework cheat, I'm messing with an NFL stats
program for a tabletop sim game. I wanted the countif stuff to see what kind
of %age of a teams total running attempts were made by each back

Now, I have a set of endurance ranges, either 5 or 6, not sure yet, and want
the number in each group to then reflect a normal Gaussian distribution with
the bulk of players in the middle category and very few at each end

I can remember 1 std dev either side containing ~ 66% of the population and
doesn't 2 std dev cover ~ 95%?

something else is coming back to me - isn't this z-scores, with the mean at
"x=0" effectively where the normal is centred around?

anyway I know the mean and stdev of the values, so hopefully there is a way
to quickly calculate the bounding limits of any arbitrary (equal) set of
divisions of the population