how to make row in table readonly based on column value

Hi Sir,

   Lets say I have table with following values

order#       cust_address   status             qty

100          123 main st       New                 3

101           111 joe st         Closed             4

102           112 main dr      Open               5

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My requirement is , when I get these records in oracle form10g, I need to make sure "Closed" status record is only display only and other than Closed status records should be editable.

On implementation I perform following task

     In when-form-instance , I wrote , execute_query;

     Then in post_query I set property to Update property to false .

It's not working the way I need.

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Then I put execute_query at block level and use pre-block or post-block to set Update property for that row items as false. it's not working.