Is the character a valid second or later character of a VBA identifier (a..z, A..Z, 0..9, _) ?
The character to evaluate
xf.Str.IsIdentifierChar("%") => False
xf.Str.IsIdentifierChar("5") => True
xf.Str.IsIdentifierChar("F") => True
xf.Str.IsIdentifierChar("_") => True