fejl i linje!

Er der nogen der kan finde ud af hvad fejlen i denne kode er?

fejlen er i linjen: fso.CopyFile fullfilname, BackupDir, True

kode:
Private Sub cmdBackup_Click()
    Dim fso As FileSystemObject
    Set fso = New FileSystemObject
    Dim i As Integer
    Dim BackupDir As String
    BackupDir = txtBackupDir.Text & Format(DateTime.Now, "yyyy-MM-dd HH-mm-ss")
    fso.CreateFolder BackupDir
    For i = 0 To lstBackup.ListCount - 1
        Dim sti As String
        sti = lstBackup.List(i)
        If Right(sti, 1) = "*" Then 'mappe
            Dim fullmappename As String
            fullmappename = Mid(sti, 1, Len(sti) - 2)
            fso.CopyFolder fullmappename, BackupDir, True
        Else
            Dim fullfilname As String
            fullfilname = Mid(sti, 1, Len(sti))
            fso.CopyFile fullfilname, BackupDir, True
        End If
    Next i
    MsgBox "Backup foretaget!"
End Sub