Hi Tazan,

Reason : In your code you have not written your domain inside "double quote". Thats why you got an error " % undefined as prefix " 

Solution :

You can use %(xxx)d inside domain. But you need to use as like below.

1) If you are giving domain inside any field definition then you need to define domain as like below.

<field name="M2O_field" domain="[('carrier_id','=',%(fbv_vexpress.carrier_vexpress)d )]" />

2) If you inherit any view and add just domain attribute then you need to define domain as like below.

<field name "M2O_field" position="attributes">
    <attribute name="domain">"[('carrier_id','=',%(fbv_vexpress.carrier_vexpress)d )]"</attribute>
</field>

I hope you are getting what exactly I want to explain. So, in your case (2) is applicable.

Thanks.