Assuming the OP lacks the enviable programming skills of BlackBox, is not interested in developing the code to get a combination of AutoLISP and Scripting to operate on all of the files in a particular folder, and conceding that Melanie is correct (as if that were ever really necessary), I would suggest using ScriptPro (November, 2010) to handle the multiple file part and developing a simple script to run the Express Tools command, using the -BLOCKREPLACE command line version.