Laufzeitfehler '1004': Anwendungs-und ...

Sub RiskAss()
Dim xlApp As Excel.Application
Dim wb As Excel.Workbook
Dim ws As Excel.Worksheet
Dim datein As Integer
Dim MD As Worksheet
Dim OV As Worksheet
Dim TR As Worksheet
Dim FD As Worksheet
Dim FSO As Object
Dim fo As Object
Dim myStr As String
Dim path As String
Dim folder As String
Dim i As Integer
i = 1
Dim h As Integer
folder = "path/"
Set FSO = CreateObject("Scripting.FileSystemObject")
Set fo = FSO.getfolder("//Test")
datein = fo.Files.Count
For Each FSO In fo.Files
Set MD = ThisWorkbook.Sheets(1)
Set OV = ThisWorkbook.Sheets(2)
Set TR = ThisWorkbook.Worksheets("Tab. Risk")
i = i + 1
Set xlApp = CreateObject("Excel.Application")
If xlApp.Workbooks.CanCheckOut(folder & FSO.Name) = True Then
xlApp.Workbooks.Open (folder & FSO.Name)
'xlApp.Workbooks.checkout docCheckOut
Set wb = xlApp.ActiveWorkbook
Set ws = wb.Worksheets("Single R&O Record")
xlApp.Visible = True
'****************************Copy Data************************************
'1) No.
MD.Cells(i, 1).NumberFormat = "@"
MD.Cells(i, 1) = ws.Cells(1, 29)
OV.Cells(i, 1).NumberFormat = "@"
OV.Cells(i, 1) = MD.Cells(i, 1)
TR.Cells(i, 1).NumberFormat = "@"
TR.Cells(i, 1) = MD.Cells(i, 1)
... hier ca. 20 dieser Blöcke
'dann das workbook schließen...
wb.Close savechanges:=False
xlApp.Quit
Set xlApp = Nothing
Set wb = Nothing
Set ws = Nothing
Set MD = Nothing
Set OV = Nothing
Set TR = Nothing
End If
Next
End Sub