Checking if a file is open before attempting to open it

[Talat]

Hi,

I have the following short code to auto open a macro file when teh main fiel is is opened.

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Sub Auto_Open()
'
' Auto_Open Macro


Workbooks.Open Filename:="G:\PUBS\PP-MS\INVOICES\SALEMAC.xlm", Notify:= _
False
ActiveWindow.Visible = False
End Sub

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I want to change this code so that it frst checks if teh file is already open, and only open it if it is not. Can anyone help with it?

Thanks.

Talât