Specific macro or VBA code to hide and unhide rows

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