Sub b1()
Worksheets("Sheet1").Select
x = 1
Do While Cells(1, x) <> ""
Select Case Cells(1, x)
Case Is >= 90
Cells(2, x) = "A"
Case Is > 80
Cells(2, x) = "B"
Case Is >= 70
Cells(2, x) = "C"
Case Is >= 60
Cells(2, x) = "D"
Case Is >= 50
Cells(2, x) = "E"
Case Else
Cells(2, x) = "F"
End Select