Try something like this:

Put this in the 'ThisWorkBook' area:
Private Sub Workbook_Open()
   g_mStrPW = "ChooseYourPassword"
   MsgBox "Note: This workbook is password protected."
End Sub

Put this in the 'Sheet#' area, whichever is applicable:
Private Sub LockEM_Click()
Dim i As Long
Dim WS As Worksheet
g_mStrPW = InputBox("Password:")
On Error GoTo MyErr
For Each WS In ActiveWorkbook.Worksheets
   WS.Protect (g_mStrPW)
   If WS.Protection.AllowUsingPivotTables = False Then
   WS.Protect Password:=g_mStrPW, AllowUsingPivotTables:=True,
AllowFiltering:=True, DrawingObjects:=False, Contents:=True,
Scenarios:= _
       True
   End If
Next
MsgBox i & " errors while protecting", vbInformation

Exit Sub
MyErr:
i = i + 1
Resume Next
End Sub

Private Sub UnLockEM_Click()
Dim i As Long
Dim PW_unlock As String
Dim WS As Worksheet
PW_unlock = InputBox("Password:")

On Error GoTo MyErr
If PW_unlock <> g_mStrPW Then
MsgBox "Error: Failed to unprotect worksheets! Please check password
in ThisWorkBook and retry."
Exit Sub
Else
For Each WS In ActiveWorkbook.Worksheets
   WS.Unprotect (PW_unlock)
Next
  MsgBox i & " errors while unprotecting", vbInformation
Exit Sub
MyErr:
i = i + 1
Resume Next
End If
End Sub

This code will lock or unlock the entire workbook - no changes to
cells can be saved, no buttons can be pressed.