title: run a macro to change a cell after a value update
body: <p>i'm clueless, i'm trying to build a code that input a prefix to a cell value after i change that cell, i mean i'll select a cell and input "342" for example, after i update that value i want the private sub to change that cell value to "GO-342", i've tried this, but it dosen't work.</p>
  
  <pre><code>Private Sub Worksheet_Change(ByVal Target As Range)
  If Target.Address = "$D$3" Then
  
  If Left(Range("D3"), 2) = "GO" Then Exit Sub
  
  Range("D3") = "GO-" &amp; Range("D3")
  
  End If
  End Sub
  </code></pre>
  
  <p>the entire code:</p>
  
  <pre><code>    Private Sub Worksheet_Change(ByVal Target As Range)
  
  'Cabeçalho
      Dim rng As Range
      Set rng = Range("D3,D5,I3,O3,O5,O7,X3,X5")
      If Intersect(Target, rng) Is Nothing Then Exit Sub
      For Each R In rng
          If R.Value = "" Then
              Exit Sub
          End If
      Next R
      Create
  
  'Km
      Dim rng1 As Range
      Set rng1 = Range("X3,X5")
      If Intersect(Target, rng1) Is Nothing Then Exit Sub
      For Each R In rng1
          If R.Value = "" Then
              Exit Sub
          End If
      Next R
      Km
  
  'GO
      If Target.Address = "$D$3" Then
      If Left(Range("D3"), 2) = "GO" Then Exit Sub
      Application.EnableEvents = False
          Range("D3") = "GO-" &amp; Range("D3")
      Application.EnableEvents = True
      End If
  
      End Sub
  </code></pre>
  
  <p>"Cabeçalho" and "Km" works but "GO" dosen't</p>