[ORACLE FORMS] Text Item

Hello,

I begin in oracle forms develeppement and I have a problem with data-block and text-items.
 I want make a window to modify a record of the users table. It is composed of text items and a button 'modify'. I don't connected the data-block to the database because I want to make the update manually with a trigger by clicking on the button 'modify'. When I want to modify a field through a text-item I have the following error :

FRM-40200: Field is protected against update.

Or no fields are linked at the database and the data-block too. To try I set the 'Allow Update' property of all text-items to 'Yes' but nothing append.

Does somebody can help me beause I swim.

Thank you.

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ben