We use Minitab, which is a great statistical product, for our capability studies... however, it's not free... I think we paid about $1000 USD for it a few years ago.
You can probably get 80% of the way there by plotting a histogram and visually comparing it to the standard normal curve. For example, it should have a single peak, centered at the mean, and the tails should be similar in size to each other. Many manufacturing processes are not normal, and often there are simple reasons. For example, if you have 2 or more process streams (e.g. 2 different dies or molds), you may get a bi-modal
distribution. If this occurs, you should do your SPC on the two dies or molds separately.
Another problem that may happen is that the distribution may be skewed, if for example it's not possible for a negative dimension to occur. We have this problem when we do SPC for flatness; it's not possible to have negative flatness.
If you're really determined, I think that you could use the chi squared distribution to test the normality of the distribution. The chi square
distribution is built into excel. I've never done this in Excel but it shouldn't
be that difficult.
It is well worth the effort to verify that a distribution is normal... most of SPC is based on the assumption of normality, and if the distribution is not normal,
you will be wasting your time and confusing yourself if you use statistics
when the assumption is not accurate.
Regards,
Brad