Windows(Filename).Activate

I write my macro like this...

 
Private Sub CommandButton1_Click()
Filename = Application.GetOpenFilename
Workbooks.Open Filename:=Filename
Windows(Filename).Activate
     Range("A1").Select
     Range(Selection, Selection.End(xlToRight)).Select
     Range(Selection, Selection.End(xlDown)).Select
     Selection.Copy
 
Windows("Rofin Pareto1.xls").Activate
     Sheets("Raw Data").Range("A1").Select
     ActiveSheet.Paste
End Sub

but when come to :Windows(Filename).Activate"..it will pop out to debug wit error..."Subcript out of range"...any1 can help me...urgent!

it also not work with the filename without space....i did not open the file also during run...any idea?