Highlight Cells modified manually and not done via macro. - vba

Question

I have been doing a little bit of research if its possible to highlight cells which have been manually amended (by typing in the information) as oppose via marco. What i really came across was track changes which might not apply in this situation
Scenario
I have a macro which runs each time certain cells are double clicked. When a cell is double clicked a timestamp is provided, which is perfectly fine.
Problem
I am trying to aviod the situation were a user tries to amend the time stamp manually, or any of that information in that relevant cell. I am trying to aviod using the methdology of locking cells once update.
Solution to be achieved.
Is it possible that if a cell has been manually updated by user that its highlighted. However if it has been update through the use of the macro thats ok.
Code
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
Application.EnableEvents = False
With Target
If .Column = 4 Then
Select Case .Row
Case 20, 24, 25, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 40, 42, 43, 44, 54, 55, 56, 58, 59, 61, 62, 63, 64, 65
.Value2 = "Prepared By" & " " & Environ("Username")
.Value2 = .Value2 & " " & Format(Now, "yyyy-MM-dd hh:mm:ss")
End Select
End If
End With

Answer 1

The simplest solution to this would just to be enforce any changes to your selected cells with the change event. I assume the double click aspect is to make it more user friendly for the input so we won't remove that, rather duplicate it:
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
With Target
If .Column = 4 Then
Select Case .Row
Case 20, 24, 25, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 40, 42, 43, 44, 54, 55, 56, 58, 59, 61, 62, 63, 64, 65
.Value2 = "Prepared By" & " " & Environ("Username") & " " & Format(Now, "yyyy-MM-dd hh:mm:ss")
End Select
End If
End With
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)
Dim cell As Range
If Target.Cells.Count = 1 Then
With Target
If .Column = 4 Then
Select Case .Row
Case 20, 24, 25, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 40, 42, 43, 44, 54, 55, 56, 58, 59, 61, 62, 63, 64, 65
.Value2 = "Prepared By" & " " & Environ("Username") & " " & Format(Now, "yyyy-MM-dd hh:mm:ss")
End Select
End If
End With
Else
For Each cell In Target.Cells
With cell
If .Column = 4 Then
Select Case .Row
Case 20, 24, 25, 27, 28, 30, 31, 32, 33, 34, 35, 37, 38, 40, 42, 43, 44, 54, 55, 56, 58, 59, 61, 62, 63, 64, 65
.Value2 = "Prepared By" & " " & Environ("Username") & " " & Format(Now, "yyyy-MM-dd hh:mm:ss")
End Select
End If
End With
Next cell
End If
End Sub