From Microsoft Help:
The following is a list of syntax rules that you need to be aware of when you create and edit names:
Valid characters - The first character of a name must be a letter, an underscore character (_), or a backslash (\). Remaining characters in the name can only be letters, numbers, periods, and/or underscore characters.
Note - You cannot use the uppercase and lowercase characters "C", "c", "R", or "r" as a defined name, because they are all used as a shorthand for selecting a row or column for the currently selected cell when you enter them in a Name or Go To text box.
Cell references disallowed - Names cannot be the same as a cell reference, such as Z$100 or R1C1.
Spaces are not valid - Spaces are not allowed as part of a name. Use the underscore character (_) and period (.) as word separators, such as, Sales_Tax or First.Quarter.
Name length - A name can contain up to 255 characters.
Case sensitivity - Names can contain uppercase and lowercase letters. Excel does not distinguish between uppercase and lowercase characters in names. For example, if you created the name Sales and then create another name called SALES in the same workbook, Excel prompts you to choose a unique name.
