Via the Dynamics UK GP Blog, there is a Security Synchronization Utility now available for GP 10 and Business Portal. The link on their site is a Partnersource link, I don’t know if there’s a Customersource path to the file or if you’ll need to contact your partner for this.
Business Portal Security Sync Utility
Install, Upgrade & AdminMicrosoft & the GP EcosystemGP 10
Archived post from 2008. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.