Populating IDCUSTs

IDCUST sequences begin at different points for different job types. This prevents multiple subjects from having the same IDCUST during any given season. 

IDCUSTS are prefixed with the School Code (####) and the school year (23-24) - For example "99992324" would be the prefix for the Acme School (9999)

The only exception to this rule is GRAD jobs that use just the current year as the prefix (24 - in the spring)