How can i search unreplied tickets?

I want to search all Tickets which have replies from requestors but are not answered by our staff.

I have tried adding this in the TicketQL Query:
Told < LastUpdated
but does not seem to support this type of query.

We managed to do this via a SCRIP which sets a ticket priority if correspondence was made by a staff member or a customer.

return 0 unless ($self->TransactionObj->Type eq 'Correspond' || $self->TransactionObj->Type eq 'Create') ;

my $email = lc($self->TransactionObj->CreatorObj->EmailAddress);

if (index($email, '') == -1)
} else 

return 1;

And now we can create a search based on Priority.
Priority setting was the quickest way for us, but it can also be done with a Custom Field.