Enable/Disable vba code

I use the following code to hide rows which contain a specific value in a cell.
In the code below the row will be hidden when the value 1 is placed in any row in column E.

This is exactly what I need, although I want to have the option to hide and unhide the rows.
For example when entering a specific value in another cell like: in A1 the word hide or unhide to hide or show all rows.

How do I extend the script below to achieve this ?

Private Sub Worksheet_Calculate()
 Dim LastRow As Long, c As Range
 Application.EnableEvents = False
 LastRow = Cells(Cells.Rows.Count, "E").End(xlUp).Row
 On Error Resume Next
 For Each c In Range("E1:E" & LastRow)
    If c.Value = 1 Then
         c.EntireRow.Hidden = True
     ElseIf c.Value = 2 Then
         c.EntireRow.Hidden = False
     End If
 Next
 On Error GoTo 0
 Application.EnableEvents = True
 End Sub