Does the CXlOper contain a multiple reference?
[C++]
BOOL IsMRef() const;
Returns TRUE if the CXlOper contains a multiple reference, 
            FALSE otherwise.
Header: xllplus.h
CXlOper Class 
					  | CXlOper Methods			 
					  | CXlOper::IsArray()			 
					  | CXlOper::IsDouble()			 
					  | CXlOper::IsError()			 
					  | CXlOper::IsBool()			 
					  | CXlOper::IsString()			 
					  | CXlOper::IsEmpty()			 
					  | CXlOper::IsInt()			 
					  | CXlOper::IsSRef()			 
					  | CXlOper::IsMRef()			 
					  | CXlOper::IsRef()