SQL & PL/SQL :: Fetching The Table Using Concatenated Values

I am trying to pass the concatenated value as parameter to the select statement. But it is not returning the results.

If i pass mytrx(1) := '123' it is working fine. It is failing when i pass more than one value.

Table script

create table xxtesttrx (trx_number varchar2(50));

insert into xxtesttrx
values('123');
insert into xxtesttrx
values('456');

Code

declare
-- declare the table type
TYPE xxtest IS TABLE OF
xxtesttrx.trx_number%Type
INDEX BY BINARY_INTEGER;
[code]......