Quoting from Excel help:
Guidelines for names
What characters are allowed? The first character of a name must be a
letter or an underscore character. Remaining characters in the name can be
letters, numbers, periods, and underscore characters.
Can names be cell references? Names cannot be the same as a cell
reference, such as Z$100 or R1C1.
Can more than one word be used? Yes, but spaces are not allowed.
Underscore characters and periods may be used as word separators — for
example, Sales_Tax or First.Quarter.
How many characters can be used? A name can contain up to 255 characters.
Note If a name defined for a range contains more than 253 characters, you
cannot select it from the Name box.
Are names case sensitive? Names can contain uppercase and lowercase
letters. Microsoft Excel does not distinguish between uppercase and lowercase
characters in names. For example, if you have created the name Sales and then
create another name called SALES in the same workbook, the second name will
replace the first one.
