Keeping casual users out of the navigation pane

How can I turn off access to the navigation pane without using runtime?
One of my users has chanced his way into the database programming and I want to turn off that ability.

youd 'SAVE AS' the database into an .ACCDE
then they cannot get into the code.
also
hide the db.

I use this as the 1st statement in the autoexec macro: RunCode HideDB()
so users cannot see the tables/queries/etc.
The 2nd statement is OpenForm MainMenu

Code:

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Public Function HideDB()
    DoCmd.SelectObject acTable, , True
    DoCmd.RunCommand acCmdWindowHide
End Function

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