Returns the number of cells in an array
[C++]
USHORT GetVectorCount() const;
This function returns the total number of cells contained in an OPER.
Use this function with VectorCell() to iterate the cells in a vector. If the OPER is not a vector (i.e. contains more than row and more than column) 
            then the return value may be subject to overflow (because it is greater than 2^16) 
            and will therefore be unreliable.
Header: xllplus.h
COper Class 
					  | COper Methods			 
					  | COper::VectorCell()			 
					  | COper::IsVector()