FWIW - I like to separate my code from the data. This way I can hide the code file from view and have it open as read-only (since it is fixed code it will not be updated during use) With the file hidden it will not show in the workbooks list. I keep master copies of programs so if something gets altered I can replace it quickly.
Password protection and saving as a .xla gives more protection, but for internal stuff hiding and using read-only works good without having to keep up with passwords.
Here's utility code I use to to hide, save, and close a code file after I've finished editing and testing.
Code:
Sub CloseNhide()
Dim visbook As Object
Set visbook = ActiveWorkbook
ActiveWindow.Visible = False
visbook.Save
visbook.Close
End Sub
/