code in X++ on an event handler of a table

provide me a code for the below validation which is when i save a record or records error should be thrown if txt field of table ledgerjournaltrans is empty and along with it if i select multiple records and if they have same data in voucher field which belongfs to table ledgerjouranltable and if in any one record txt field is field then no error should be thrown otherwise diff voucher then i want error.. so provide me code for it in x++