Sub TestFileOpened()
If IsFileOpen("c:\Book2.xls") Then 'Pfad + Dateinamen anpassen
MsgBox "File already in use!"
Else
MsgBox "File not in use!"
Workbooks.Open "c:\Book2.xls" 'Pfad + Dateinamen anpassen
End If
End Sub
Function IsFileOpen(filename As String)
Dim filenum As Integer, errnum As Integer
On Error Resume Next
filenum = FreeFile()
Open filename For Input Lock Read As #filenum
Close filenum
errnum = Err
On Error GoTo 0
Select Case errnum
Case 0
IsFileOpen = False
Case 70
IsFileOpen = True
Case Else
Error errnum
End Select
End Function