klimin on "[Plugin: Contact Form 7] Using fields in the "Additional Settings" section"

I noticed, that I cannot use fields in the "Additional Settings" section.
For example, I have text field [text* field-url], and next fragment of code doesn't work:

Additional Settings
on_sent_ok: "location = '[field-url]/subpage';"

:(

http://wordpress.org/plugins/contact-form-7/