I would suggest you to work with specific adressing of the Workbooks and Sheets. So you could be sure that you are all time inside the right Workbook / Sheet.
Here an example what I have used :
Dim oWB, aWb As Workbook
Dim aSh As Worksheet
QDatei = RechnungsNr + ".xls"
Quelldatei = Modul1.PrgDaten_Pfad + QDatei
PrgDatei = Modul1.Programm_Name
Sheets("Temp-Daten").Cells.Delete Shift:=xlUp
Set aWb = ActiveWorkbook
Set aSh = ActiveSheet
Set fs = CreateObject("Scripting.FileSystemObject")
FileExists = False
If fs.FileExists(Quelldatei) Then
Set oWB = Workbooks.Open(Filename:=Quelldatei, ReadOnly:=True, UpdateLinks:=False)
FileExists = True
ElseIf fs.FileExists(Quelldatei + "m") Then
Set oWB = Workbooks.Open(Filename:=Quelldatei + "m", ReadOnly:=True, UpdateLinks:=False)
FileExists = True
End If
If FileExists Then
aWb.Activate
aSh.Select
ActiveSheet.Unprotect
[C8] = oWB.Worksheets(1).[C8]
[c9] = oWB.Worksheets(1).[c9]
[c10] = oWB.Worksheets(1).[c10]
Of course it isn't complete - but it shows you how to do it ...