How to set a field value when the value of another field changes

Summary:

Hi community,

I would like to set the value of “Category” when an Asset is selected.

Note that “Category” is a custom field.

I was trying to use a event listener for custom assetEvent in the CustomerWorkOrders layout

and then get the field value of the asset using Get Field Value CX Service function (I would like to know what value I need to set in Object Context for getFieldValue):

but I don't get any value:

Once the value is retrieved, I want to pass it to the category using the Set Field Value function.

How can I do this?