The import command can either take a hard coded file path, or a variable representing a full file path. So you script can calculate that file path, using the prefix and the calcualted date part. You then specify just the variable name in the import script step.
Just found the set varible command - getting there!
Thanks again for the help!
Buck may be calculating too hard,
Most likely you put too much into the select file dialog. The select file dialog does NOT perform calculations. It can use either a fully formed path or a variable. NOT pieces of both.