Scripting Xcode 3: opening files in main project window

First, I have an automator workflow that does nearly everything I want it to do at:

If you run the workflow, it will first ask for a text file which, on each line, contains the full path to a file you want to open within Xcode. It will then close every open file in Xcode and open the files in the text file.

I have the all-in-one layout, but when this script runs, it opens the files in a separate window and I want them opened in the main window.

Any suggestions on how I can do this?

Any other / different clever solutions to do what I am trying to do with this workflow (i.e. just have a small set of files in the file history which I can easily switch between since the file history rapidly grows out of control since I still need it to remember an unlimited set of files)?