How set focus to Linked Issues?

I try via behaviour add issue in field “Linked Issues” for this i use this code

def cutomField=getFieldById("customfield_10400");
String value=(String)cutomField.getFormValue();
def sum=getFieldById("issuelinks-issues-textarea");

but link doesn’t save after create issue. Link would have save if I’d click on field “Linked Issues”. How set focus field after fill that would user click other field and link save? Thanks.
Version jira 5.0.3