Customize date/time format in report file name

I want my TestStand UUTs reports (Batch process model) to have file name of the following format:

UUT_yyyyMMddHHmmss.txt

In particular, I want to use year-month-day for the date component, and 24-Hr format for the time component.  I'd also like to remove the [ ] that the default file name format includes.

The Report Options -> Report File Pathname dialog does not seem to allow this level of configuration, and I cannot find where is the appropriate place to make this change.  Can I do this in a sequence file callback in my client sequence file, or do I need to modify the process model itself?  I've also already made changes to ReportGen_txt.seq for customizing the internal format of my report, so I can make the change there as well if needed.