Hi,
if you can unload the schema manually from the LASR tables tab of the Administration page, you can always make VA to generate a .sas file of that action, on the File-->Preferences options. When enabled, this will generate the .sas file of any action on LASR servers or LASR tables (start/stop servers, load/unload tables).
With the .sas file, you can generate a bat file or just generate a sas command on your scheduler, and schedule as you wish.