The following code works perfectly on my machine. The custom toolbar
is only visible when one specific sheet is active and disappears when
I switch to another sheet or another workbook. But when the WB is
opened on someone else's machine the toolbar appears and will stay
visible when another WB is activated and then a second copy of it
appears when switching back to the original WB.

Module1

Private Sub Auto_Open()
Call CreateMyCustomToolbar
Worksheets("Database").Activate
End Sub

Public Sub CreateMyCustomToolbar()
Dim i As Long
Dim macro_names As Variant
Dim cap_names As Variant
Dim tip_text As Variant

Call Remove_ToolBars

Stuff to create tool bar goes here

End Sub

Sub Remove_ToolBars()
On Error Resume Next
Application.CommandBars("MyCustomToolbar").Delete
On Error GoTo 0
End Sub


[Sheet4(Database)Code]

Private Sub Worksheet_Activate()
CommandBars("MyCustomToolbar").Visible = True
End Sub

Private Sub Worksheet_Deactivate()
CommandBars("MyCustomToolbar").Visible = False
End Sub


[ThisWorkBook(Code)]

Private Sub Workbook_Activate()
Call CreateMyCustomToolbar
End Sub

Private Sub Workbook_Deactivate()
Call Remove_ToolBars
End Sub