Mahmoud off SQL to calculate Inventory Balance Between Two Dates. One caveat, this relies on the HITB tables which may not be populated if you’ve upgraded from earlier versions of GP and never run the HITB reset tool.
Dynamics GP Essentials: Inventory Balance Between Two Dates
Archived post from 2013. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.