Is there a better way to express the following formula?
I'm in the process of upgrading an old spreadsheet and will have to increase
the future range in a more efficient manner than stated, but am having
trouble!

=IF(AND(ISNUMBER(Y679),ISNUMBER(Y680),ISNUMBER(Y68 1),ISNUMBER(Y682),ISNUMBER(Y683),ISNUMBER(Y684),IS NUMBER(Y685),ISNUMBER(Y686),ISNUMBER(Y687),ISNUMBE R(Y688)),Y679+Y680+Y681+Y682+Y683+Y684+Y685+Y686+Y 687+Y688,"not available")

TIA