Data Loader

We are using the Data Loader to import serveral files into the Opportunity object nightly.  Currently we are using a batch file to schedule the imports, but one file has to complete before another file can be loaded b/c everything is being imported into the Opportunity object.  We can use a timed pause inbetween files, but would prefer the batch file to execute the next file immediately after the previous file finishes importing.  Does anyone know if this is possible, and, if so, how?

Thanks!