How can I update 2 Jira cloud custom fields through ScriptRunner?

Question

Hoping to get help from someone on ScriptRunner. My knowledge with ScriptRunner is next to nothing.

My objective is to update 2 custom fields (Functional area and Resolver group) based on the values selected from the cascading list field (Issue category). And I want this to happen only when the Issue category is updated. Something like...

when field Issue category updated:

If Issue category parent value = X and child value = Y
  vArea = 'Technology'
  vResolver = 'IT Service Desk'
If Issue category parent value = A and child value = B
  vArea = 'Commerce'
  vResolver = 'Sales Management'
Else
  vArea = 'Other'
  vResolver = 'Other'

Then update custom field Functional Area = vArea; custom field Resolver group = vResolver

Greatly appreciate your help.

Cheers,

Expecting to update the 2 custom fields