How do I add a permanent number format?

[Roy]

Every time, every page, every column, I must enterthe following:

yyyy-mmdd ddd hh:mm:ss AM/PM
yyyy-mmdd+hh:mm

because I use both number formats quite often. If there is a way to add
these fields to the permanent database of number formats, I would appreciate
someone informing me on how to perform such a function. Thank you.

Also, if someone can tell me how to make this number format the default
format for all of Office, that would be very much appreciated also. Thank
you.

Roy