Oracle Forms

I have this layout

http://img339.imageshack.us/img339/975/capturetbo.png

and a post trigger insert and update

                IF  :item1 IS NULL
		AND :item3 IS NOT NULL THEN
				alert_id := FIND_ALERT('blank_alert');
				SET_ALERT_PROPERTY(alert_id,ALERT_MESSAGE_TEXT,'Item3 must have a value.');
				v_alert := SHOW_ALERT(alert_id);		
				RAISE Form_trigger_Failure;
		END IF;

My problem was as it fires, the cursor will be on the item1.
I've already use

SET_ITEM_INSTANCE_PROPERTY
NEXT_ITEM
GO_ITEM

but it was all illegal. The cursor must be in the item3.

Don't question me why I do not set the item3 to required and why post triggers.
It is just that. It is the requirement.
Any bright Idea? Thanks!

And even when-validate-item triggers. It must be post triggers.
Is it possible? Thanks.

Edited by: reppihsrow on Feb 19, 2013 6:02 PM