web-item url custom field fetch

[Dipti Desai]

Hi, we have a web-item that clones existing ticket to another project. I am trying to auto-fill some of the fields using following url. How can I capture the parent issue's custom field's value? so, in the example below, what should "parent-issue-some-customfield-value" be?

<link linkId="prs-ki-web-item-link">/secure/CreateIssueDetails!init.jspa?pid=12400&amp;issuetype=10802&amp;summary=${issue.summary}&amp;customfield_12801=${issue.key}&amp;customfield_12802=${parent-issue-some-customfield-value}</link>

Thanks