sum of field value of subtasks for parent

[Marzi Goodarzian]

Hello

I wrote a script field that show "time spent" for every subtask, now I want collect (sum) this field from all of subtasks for a parent shown  in parent field:

1)return time spent based on Hourse for subtask:

****

import com.atlassian.jira.issue.changehistory.ChangeHistoryManager;

import com.atlassian.jira.issue.changehistory.ChangeHistory;

import com.atlassian.jira.model.ChangeItem;

import com.atlassian.jira.issue.history.ChangeItemBean;

import com.atlassian.jira.issue.changehistory.ChangeHistoryItem;

import com.atlassian.jira.component.ComponentAccessor;

import com.atlassian.jira.issue.*

import com.atlassian.jira.issue.worklog.Worklog

ChangeHistoryManager changeHistoryManager =ComponentAccessor.getChangeHistoryManager();

List <ChangeItemBean> changeItemBeans= changeHistoryManager.getChangeItemsForField(issue, "timespent");

  return ((changeItemBeans.last().getToString() as Long)/3600).toDouble()

2)sum of subtasks field(LogSpent) for parent:

*******

import com.atlassian.jira.component.ComponentAccessor

import com.atlassian.jira.issue.Issue

import com.atlassian.jira.issue.fields.CustomField

//14521=logSpent Field ID

CustomField LogSpent = ComponentAccessor.getCustomFieldManager().getCustomFieldObject(14521);

double totalSum = 0;

issue.getSubTaskObjects().each {subtask->

    if(subtask.getCustomFieldValue(LogSpent) != null)

       totalSum +=  subtask.getCustomFieldValue(LogSpent);

}

return totalSum

I also used this:

totalSum +=  Double.parseDouble(subtask.getCustomFieldValue(LogSpent));

but in second script show error and can't sum these values, How can fix it?

Thanks for help