Forms :: Create A Form For Ordering

i create a form for ordering>>>that the person can enter his/her information and isbn book to make the order,but the order id i make it sequentially! well first of all i create a data-block and i insert only the oid in trigger when-new-item-instance..i had create the sequence:

declare
create sequence seq1
start with 90
increment by 10;
end;

and i make a view form such of fields that user can enter a details o what he/she want to order!!

1- is that enough?

2- it seems there is an error in creating the sequence?? wrong way to create the sequence!!