I want to start with a simple file with one data table linked to analyses and graphs. Then I want to write a script that duplicates this family, importing new data each time.

The trick is to use the DuplicateFamily command (new to Prism 4).

Look at this file, which zips together a script, Prism file, and data files. This is a zipped file, so you'll need unzipping software. The script assumes that all the files are in C:\TEMP. You can edit it to use other locations.

There was a bug in Prism Windows up to 5.03 where the DuplicateFamily command would always add a prefix to sheet names. Starting with 5.04, you can use the command DuplicateFamily ""  (two quotation marks, with no spaces between them) to duplicate sheets with no prefix before the duplicated sheet names.