Need Filtered Lookup based on primary entity fields in CRM 2013

Hi All,

As we know CRM 2013 has given a nice feature 'addCustomFilter' method which we can use with addPreSearch to filter lookups on the form.

But this works only if we are filtering the lookup values on the basis of any other attribute present on the same form. Is there any way where Primary entity's fields can be used in fetchxml filter. For eg. I have entity 1 lookup on entity 2's form and I need to filter this lookup on the basis of attribute present in entity1. How can I achieve that?

Any help  is highly appreciated.

Thanks