Rails 3 ActiveAdmin. How to use ONE field for SIX columns on a search in Active Admin?

Question

How can I add a custom filter or create a custom search field with ActiveAdmin?

I need to generate a report on wire transfers. There are these fields in the Invoices model

• wire_transfer_1_ar
• wire_transfer_2_ar
• wire_transfer_3_ar
• wire_transfer_1_customer
• wire_transfer_2_customer
• wire_transfer_3_customer

So I have this

filter :wire_transfer_1_ar
filter :wire_transfer_2_ar
filter :wire_transfer_3_ar
filter :wire_transfer_1_customer
filter :wire_transfer_2_customer
filter :wire_transfer_2_customer

So when a wire transfer is found, then I can click a link to generate a report.

How can I use only ONE field, to search for all those 6 fields?