I'm afraid I'm not following what you're trying to do. If you simply want to copy (or move) files from one folder to another, there are several ways to do so without creating a custom button. One way is to set up a dual pane lister where you select the files you want to copy or move in the source, and then drag and drop them to the destination pane (holding down CTRL if you want to copy them).
I have directories all containing downloads I want to combine. I want to drag a directory's files into another directory instead of moving that folder into the other folder. For example:
folder a>
file1
file2
folder b>
file3
file4
would result in
folder a>
file1 thru file4
instead of
folder a>
file1
file2
folder b
file 3
file 4
I don't need to do multiple folder support or I could just make a control drag drop do this.