There is another way of doing this in the workflow script.
At the step where you open the data table, rather than have the script as Open ("12_09") - edit it to:
browse = pick file();
open(browse)
When you run the workflow it will prompt you to select the appropriate file when the workflow gets to that step.
If you are using the table at multiple steps you can have the script as:
browse = pick file();
open(browse) << save ("XXX")
and then just change all subsequent sections of the script that ask for "12_09" to "XXX"