Calculated field with runtime Lookup function from another site

[brightlight]

How would you lookup root web application site collection's root web from a different site collection?

1. For example, i have nintex form in site : http://sharepoint.test.com/sites/forms
2. I am using the first calculated value to lookup: http://sharepoint.test.com/sites/workflows, and i am able to successfully get the values: lookup("/sites/workflows|listname", "Title", ""+NamedControl+"", "Designer")
3. But when i try to lookup the root web application site collection's root web then i do not get anything: lookup("/|listname", "Title", ""+NamedControlFromNumber2BulletPoint+"", "Date")