Private Sub Worksheet_Calculate()
If UCase(Range("I4").Text) = "HIDE" Then
    Range("A33:A41").EntireRow.Hidden = True
ElseIf UCase(Range("I4").Text) = "UNHIDE" Then
    Range("A33:A41").EntireRow.Hidden = False
End If
End Sub
Place this in the sheet module behind Blad 1 (right click the tab--> view code --> Paste code).