Rowscopy Question

I have 2 datawindows that I wanted to copy and move rows between. Its failing with a -1

They both have exactly the same column list but the big difference is one is built using a Select statement and the other is a External Datawindow.

I'm wanting to copy rows from the DW_1 Select statement to the external datawindow dw_2 without using a getitem and setitem but by using the rowscopy function.

Will the rowscopy and rowsmove work if the underlying data source is different but the columns are exactly the same ?

Thanks for any help