Switch your application scope to customer service management.

1. Create data lookup table as child table to dl_matcher.

2. Add 3 columns, impact, urgency and priority.

3. Use incident data lookup table as reference (u_dl_priority)

4. Update 3 columns created in step 2 to have choice lists point to task or case choice options, you have to in advanced vide.

5. Create data lookup definition

add setter and matcher fields

set always replace on priority matcher field.

1. Add entries to lookup table created in step 1 based on the priority matrix as per requirements.

2. Test the changes in case form.

Reference : https://docs.servicenow.com/en-US/bundle/tokyo-platform-administration/page/administer/field-adminis...

Video :

Code : https://developer.servicenow.com/connect.do#!/share/contents/3287388_case_priority_lookup?t=PRODUCT_...