Assigning an activity to resources a particular resource type only when it is preferred

Hi Team,

We a particular Resource Type called In-House-Engineer (IHE) . The resources of this resource type should be assigned activities only if they come as 'Preferred' in resource preference of an activity. No activities where an IHE is not preferred should get assigned to them. Is there anyways we can handle this in routing?

We have tried creating a filter for IHE and giving assignment cost 'high' and 'highest' . But this isn't fool proof and fails for certain scenarios.

Is there any better solution how we can handle this in Routing?

Any helpful insights would be very helpful.

Thanks,

Anusree