Honestly I have done these type of things in many different ways, but the cleanest is to take the software out of the equation. Either create your own syncs or use a commercial sync software. Set-up a middle SQL database between the ERP and Kentico. Use the sync or DB triggers to push changes into the middle DB and out to the Kentico tables.
Why a middle database, because much like business logic code, it abstracts the two systems from one another and prevents having to recreate the entire connection if one side changes some how. Honestly doesn't take anymore effort and overall easier to control the sync process.