select case

Hello,

I have data in row 2 (column A to Z). I would like to add a number to row 3 (corresponding column) upon the data in row 2.

Private Sub excurate_mass()

Application.ScreenUpdating = False

Dim i As Long
For i = 1 To 26

            
If Not Cells(2, i) = "" Then

    Select Case Cells(2, i).Value

Case A
    Set Cells(3, i) = "71.037114"
    
Case C
    Set Cells(3, i) = "724"
    

End Select

Else: Exit Sub
End If

      
Next i

Application.ScreenUpdating = True

End Sub

the code is not working. any help would be appreciated.