Enable/Disbale cells of dropdown list in excel - excel

Question

I have created a simple dropdown list. It looks something like this.
Here user is allowed to have multiple selection.
I want if user has selected options other than Not Applicable, then it should disable Not Applicable cell and enable other cities to select. But if user first selects Not Applicable then other city option should be disable. Also clicking on same cell will enable and disable the cell.
For E.g. First user decides not to select any country so he clicks on Not Applicable option and automatically "New York, Berlin, Mumbai, Munich" options gets disable. But later if user decides to select City option and if he again clicks on Not Applicable then it should get disable and other countries should get enable.
Also I have associated values to the cities and I am printing values.
=SUMPRODUCT(--(ISNUMBER(SEARCH(Sheet2!A2:A6;Sheet1!A2))*Sheet2!B2:B6))
I have used follwoing multiple selection and removal code from the internet.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim xRng As Range
Dim xValue1 As String
Dim xValue2 As String
If Target.Count > 1 Then Exit Sub
On Error Resume Next
Set xRng = Me.Range("A2")
If xRng Is Nothing Then Exit Sub
Application.EnableEvents = False
If Not Application.Intersect(Target, xRng) Is Nothing Then
xValue2 = Target.Value
Application.Undo
xValue1 = Target.Value
Target.Value = xValue2
If xValue1 <> "" Then
If xValue2 <> "" Then
If InStr(1, xValue1, xValue2 & ",") > 0 Then
xValue1 = Replace(xValue1, xValue2 & ", ", "") ' If it's in the middle with comma
Target.Value = xValue1
GoTo jumpOut
End If
If InStr(1, xValue1, ", " & xValue2) > 0 Then
xValue1 = Replace(xValue1, ", " & xValue2, "") ' If it's at the end with a comma in front of it
Target.Value = xValue1
GoTo jumpOut
End If
If xValue1 = xValue2 Then ' If it is the only item in string
xValue1 = ""
Target.Value = xValue1
GoTo jumpOut
End If
Target.Value = xValue1 & ", " & xValue2
End If
jumpOut:
End If
End If
Application.EnableEvents = True
End Sub

Answer 1

Try the following (place it in the module from the sheet with the dropdown list):
Private Sub Worksheet_Change(ByVal Target As Range)
Dim searchNA As Range
Dim LRow As Long
If Not Intersect(Target, Range("A2")) Is Nothing Then
With ThisWorkbook.Sheets("Sheet2")
LRow = .Cells(.Rows.Count, "A").End(xlUp).Row
Set searchNA = .Range("A2:A" & LRow).Find(Target.Value, lookat:=xlWhole, MatchCase:=True)
If Target.Value = "Not Applicable" Then
.Range("A2:A" & LRow).Locked = True
searchNA.Locked = False
Else
.Range("A2:A" & LRow).Locked = False
searchNA.Locked = True
End If
End With
End If
End Sub
I have assumed the validation list is in Worksheet("Sheet1") and the small table with cities is in "Sheet2"