Activity Type Determination

What's the best way to determine whether an activity was created as an interaction record or a follow-up in the Webclient? I've seen the code in the Webclient that determines this (such as CL_CRM_IC_CUCOFOUP_IMPL->CHECK_IREC_OR_FOUP), but the code doesn't replicate well outside of the Webclient. (The factory method to create the BOL core object works, but several object attributes are not instantiated, and dumps occur when trying to use the object to get an entity from the GUID.)

I have interaction records that have an 'Open' status that need to be closed via LSMW, so I need to pull the open activity GUIDs from CRMD_ORDER_INDEX, detrmine if it's an interaction record, and set a new status. Thanks.