Disable Menu Commands

I need to disable the "save as" file menu command when a user opens a shared document. Upon exit I want to enable the save as so that other opened worksheets are not affected. This code works: CommandBars("File").Controls("Save As...").Enabled = False

My problem is this. I can activate this command by selecting run in the VB editor.
But I need for this action to be automatic when a user opens the worksheet. I did this in the editor:

Under general

Sub dISABLESAVEAS()
CommandBars("File").Controls("Save As...").Enabled = False
End

Sub WORKSHEET_BEFORECLOSE()
CommandBars("File").Controls("Save As...").Enabled = True
End