=IF(A1="A",B1,"")&IF(A1="B",B1*C1,"")&IF(A1="C",B1-C1,"")&IF(A1="D",B1/C1,"")&IF(A1="E",C1+B1,"")&IF(A1="F",C1,"")&IF(A1="G",B1^2,"")&IF(A1="H",C1^2,"")