Consider a custom object named Importance Priority Matrix which has records with these attributes: Order Type, Purpose of Visit, Severity, Customer Down, Importance, Priority.

Sample records in Importance Priority Matrix can be as follows:

If a work order’s Order Type is Field Service, Purpose of Visit is Repair, Priority is High, and Customer Down is True, then that work order’s Importance (custom field) should be set to 5 and Order Priority (custom field) to 90.

The above requirement can be configured as Data Lookup Rule, with a field map between Work Order (target object) fields Importance & Order Priority and Importance Priority Matrix (source object) fields Importance and Priority respectively.