It's been like forever and a day since the last time I used BGInfo, so I had to look up its options ( http://technet.microsoft.com/en-us/sysinternals/bb897557 )It seems like to me you would just need to add a custom field that was would be used for a kix calulation. Assuming that the import file is text, open the file in kix, add the custom field with the calculated date, and save the changes. Then you would rerun the bginfo either by task scheduler or admin script to re-import the settings file.
I use serialdate for this type of thing... something like
