referencing file with date/time stamp

I have a workbook in Excel 2007 that, based on a dropdown selection, goes out and finds the selected "table" file, opens it, copies a cell range, pastes it into the workbook and then closes the table file.

My question is; can I make it more specific? I don't want someone to edit the table files, so I thought that if I could also specify the date/time stamp of the file, that it would alleviate anyone tampering with them.

Any suggestions?