=IF(MONTH($K$6)<>MONTH($K$6-(WEEKDAY($K$6,1)-($AU$3-1))-IF((WEEKDAY($K$6,1)-($AU$3-1))<=0,7,0)+(ROW(K8)-ROW($K$8))*7+(COLUMN(K8)-COLUMN($K$8)+1)),"",$K$6-(WEEKDAY($K$6,1)-($AU$3-1))-IF((WEEKDAY($K$6,1)-($AU$3-1))<=0,7,0)+(ROW(K8)-ROW($K$8))*7+(COLUMN(K8)-COLUMN($K$8)+1))

You help is greatly appreciated!!!!