The value assigned is not a valid named reference. The name must begin with a letter, underscore (_), or a backslash (\).
All other characters in the name must be letters, numbers, periods, underscores (_), or backslashes (\).
The name cannot be a an A1 cell reference (1 to 3 letters followed by 1 to 6 numbers). In addition, the name
cannot be 'r', 'R', 'c', or 'C' or start with a row or column reference in R1C1 cell reference mode
('R' followed by 1 to 6 numbers or 'C' followed by 1 to 6 numbers).
The value assigned is the name of another named reference with the same Scope.
Names are compared case-insensitively.
See the overview on Scope for details on how to access a named reference by name in formulas.