Hi,
That’s more or less how the NetDriver handles replicated object reference properties, as it periodically checks to see if these are mapped (UNetDriver::UpdateUnmappedObjects).
I don’t believe there’s any built-in event you could register to, so that would have to be custom implemented. In the case of newly mapped object reference properties, the only callback is the property’s RepNotify if it is using one (see FRepLayout::UpdateUnmappedObjects_r and FGuidReferences::UpdateUnmappedGUIDs).
Thanks,
Alex