Move All Worksheets From Book B Behind All Sheets In Book A?

I made the following code to merge 2 workbooks together.

The code is to be executed when the user has Workbook A opened. (All sheets in workbook KPISWD are supposed to be moved after all worksheets in workbook KPICustomers).

I keep getting a debug error on the code that is supposed to do the actual move and loop until it is finished with all of the sheets in Workbook B.

Code:
Dim KPICustomers, KPISWD As String
KPICustomers = ActiveWorkbook.Name

Workbooks.Open Filename:= _
"W:FacturatieKPI per periode SWD.xls"

KPISWD = ActiveWorkbook.Name

[Code] ..........