Trying to get sum of original estimates in a custom field using Jira Automation

[Farrukh Elahi]

Hi, 

I'm trying to sum original estimated hours of stories and test cases at epic level in a custom field. 

I have put the following logic but it is not working: 

When: value changes for Original Estimate

If: Issue Type is one of Story, Test Scenario

AND: Issue matches JQL

issuekey in (childIssuesOf({{issue.epic}})) AND issuetype in (Story,"Test Scenario") 

THEN: Edit issue fields

Effort estimated

set value 

issueFunction in aggregateExpression("originalEstimate.sum()")

Any help would be much appreciated.