I have 3 option buttons that populate cell K5 with "ELEV2", "STA2" OR "GRADE"

Cells D8, D10, D12, H8 and H10 are user input that will constantly be changed by user

I need help getting it to auto update when the user changes any of D8, D10, D12, H8 or H10.

Also I would like to lock H10 in the Case of ELEV2, but when I insert Range("H10").Locked = True , i get an error
Any help would be great, I am a beginner!! (Excel 2007)

Private Sub Worksheet_Change(ByVal Target As Range)
        Dim Sta1 As Integer
        Dim Elev1 As Integer
        Dim Grade As Integer
        Dim Sta2 As Integer
        Dim Elev2 As Integer
'If Target.Address = "$K$5" Then
Set MyRange = Intersect(Target, Range("K5, D8, D10, D12, H8, H10"))
If Not MyRange Is Nothing Then
    ActiveSheet.Unprotect ("Password")
    Select Case Target.Value  'Target.Value OR MyRange?
    
    Case "ELEV2"  'Calculates Elevation 2 if Elevation 2 Option Button is selected
        Range("H8,D12").Select
            With Selection.Interior
                .Pattern = xlNone
                .TintAndShade = 0
                .PatternTintAndShade = 0
            End With
        Range("H10").Interior.Color = 16777062
        Sta1 = Range("D8")
        Elev1 = Range("D10")
        Grade = Range("D12")
        Sta2 = Range("H8")
            'Elev2 = (Elev1 + (Sta2 - Sta1) * (Grade / 100))
        Range("H10").Value = (Elev1 + (Sta2 - Sta1) * (Grade / 100))
        
    
    Case "STA2"  'Calculates Station 2 if Station 2 Option Button is selected
        Range("H10,D12").Select
            With Selection.Interior
                .Pattern = xlNone
                .TintAndShade = 0
                .PatternTintAndShade = 0
            End With
        Range("H8").Interior.Color = 16777062
        Sta1 = Range("D8")
        Elev1 = Range("D10")
        Grade = Range("D12")
        Elev2 = Range("H10")
            'Sta2 = (Elev2 - Elev1) / (Grade / 100) + Sta1
        Range("H8").Value = ((Elev2 - Elev1) / (Grade / 100) + Sta1)
    
    Case "GRADE"  'Calculates Grade if Grade Option Button is selected
        Range("H8,H10").Select
            With Selection.Interior
                .Pattern = xlNone
                .TintAndShade = 0
                .PatternTintAndShade = 0
            End With
        Range("D12").Interior.Color = 16777062
   
        Sta1 = Range("D8")
        Elev1 = Range("D10")
        Sta2 = Range("H8")
        Elev2 = Range("H10")
            'Grade = (Elev2 - Elev1) / (Sta2 - Sta1) * 100
        Range("D12").Value = (Elev2 - Elev1) / (Sta2 - Sta1) * 100
    End Select
    ActiveSheet.Protect ("Password")
End If
'End If
End Sub