Specific macro or VBA code to hide and unhide rows

Try:

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim c As Range
    If Not Intersect(Target, Range("B12:B17")) Is Nothing Then
        Range("B13:B17").EntireRow.Hidden = True
        For Each c In Range("B12:B17")
            If Not IsEmpty(c) Then c.Resize(2, 1).EntireRow.Hidden = False
        Next c
    End If
End Sub

Hi louvaek

Welcome to the Forum!!!

Here's another approach

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
  Dim OldValue As String, NewValue As String
  If Target.Cells.Count > 1 Then Exit Sub
  If Not Target.Column = 2 Then Exit Sub
  With Application
    .ScreenUpdating = False
    .EnableEvents = False
    .Undo
    OldValue = Target.Value  'store old value
    If Not OldValue = "" Then
      .Undo
      .ScreenUpdating = True
      .EnableEvents = True
      Exit Sub
    Else
      .Undo
      NewValue = Target.Value     'store new value
      Range(Target.Address).Offset(1, 0).EntireRow.Hidden = False
      .EnableEvents = True
      .ScreenUpdating = True
    End If
  End With
End Sub

Hi louvaek

Here's your File with the Code embedded...

Hi Kristof

The downside of Olly's Code is that the range of Cells is fixed. If that works for you then use it.

If Not Intersect(Target, Range("B12:B17")) Is Nothing Then

I'll look at this

But if I delete it again, it doesn't hide again

Hi Kristof

There's a bit of mind numbing logic going on here, see if this works as required

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
  Dim OldValue As String, NewValue As String
  If Target.Cells.Count > 1 Then Exit Sub
  If Not Target.Column = 2 Then Exit Sub
  On Error GoTo Reset
  With Application
    .ScreenUpdating = False
    .EnableEvents = False
    .Undo
    OldValue = Target.Value  'store old value
    If Not OldValue = "" Then
      .Undo
      If Range(Target.Address).Offset(1, 0).Value = "" _
         Or Range(Target.Address).Offset(-1, 0).Value = "" Then
        Range(Target.Address).EntireRow.Hidden = True
      End If
      .ScreenUpdating = True
      .EnableEvents = True
      Exit Sub
    Else
      .Undo
      NewValue = Target.Value     'store new value
      Range(Target.Address).Offset(1, 0).EntireRow.Hidden = False
      .EnableEvents = True
      .ScreenUpdating = True
    End If
  End With
Reset:
  Application.ScreenUpdating = True
  Application.EnableEvents = True
End Sub