You can do this, but a lot is going to depend on how much effort you want to put into hiding the password that unlocks the sheets, and re-installing the password once changes have been made.
This procedure will protect all of the sheets using the password that is contained in cell A1 of Sheet3:
Code:
Sub ProtectSheets()
Dim i As Integer
Dim strPassword As String
'Get the password from Sheet3 (which could be hidden or VeryHidden)
strPassword = Sheets("Sheet3").Range("A1").Value
'Protect all of the sheets
For i = 1 To Sheets.Count
Sheets(i).Protect Password:=strPassword
Next i
End Sub
Then, this procedure will unprotect all of the sheets if the TextBox (labeled as txtPassword) contains the right password. This would go in the code for the CommandButton (labeled as cmdEnterPassword):
Code:
Private Sub cmdEnterPassword_Click()
Dim i As Integer
Dim strPassword As String
strPassword = txtPassword.Value
If strPassword = Sheets("Sheet3").Range("A1").Value Then
For i = 1 To Sheets.Count
Sheets(i).Unprotect Password:=strPassword
Next i
End If
End Sub