Disallow editing a cell once there is an entry - excel

Question

I am trying to build a log book where:
Once the operator enters information that cell should lock.
A date and time for the entry should auto populate.
I have tried several codes I found on bulletin boards, but nothing works.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim i As Integer
Application.EnableEvents = False
If Target.Column = 2 Or Target.Column = 3 Then
For i = 2 To 1000
If Cells(i, "B").Value <> " " And Cells(i, "B").Value = " " Then
Cells(i, "A").Value = Date & " " & Time
Cells(i, "A").NumberFormat = "m/d/yyyy h:mm AM/PM"
End If
Next
End If
Range("F:F").EntireColumn.AutoFit
Application.EnableEvents = True
End Sub

Answer 1

In the same article you have a solution:
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("B:B")) Is Nothing Then
On Error GoTo SafeExit
Application.EnableEvents = False
Dim bc As Range 'no sense in declaring something until we actually need it
For Each bc In Intersect(Target, Range("B:B")) 'deal with every cell that intersects. This is how to handle pastes into more than one cell
If Not IsEmpty(Cells(bc.Row, "B")) Then
Cells(bc.Row, "A").Value = Now 'Now is the equivalent of Date + Time
Cells(bc.Row, "A").NumberFormat = "m/d/yyyy h:mm AM/PM"
End If
Next bc
'Range("F:F").EntireColumn.AutoFit 'this slows things down. you may want to comment this out and just set an apprpriate column width that will handle everything
End If
SafeExit:
Application.EnableEvents = True
End Sub
I just addpat for your case on Range B:B.
Hope it helps