How to show a message in a form 'PL/SQL Button Event Handler'

Question

We need validate the sal of an employee, and if it is bigger the value musts
not be inserted.
We trying a code like the one shown in the note 134312.1 'HOW TO PASS A
PARAMETER FROM A PORTAL FORM TO A STORED PROCEDURE' and it works in the insert event of the insert button (using 'PL/SQL Button Event Handler') and it works, but we need to show a message that says the data wasn't inserted. How can we do this?
The code we used is:
declare
v_deptno scott.emp.deptno%type;
v_empno scott.emp.empno%type;
v_sal scott.emp.sal%type;
mySal scott.emp.sal%type;
v_string varchar2(256);
blk varchar2(10):='DEFAULT';
begin
select sal into mySal from scott.emp where empno=7369;
v_deptno:=p_session.get_value_as_number(p_block_name=>blk,
p_attribute_name=>'A_DEPTNO');
v_empno:=p_session.get_value_as_number(p_block_name=>blk,
p_attribute_name=>'A_EMPNO');
v_sal:=p_session.get_value_as_number(p_block_name=>blk,
p_attribute_name=>'A_SAL');
v_string:='You just inserted empno: '||to_char(v_empno) ||'to deptno ->
'||to_char(v_deptno);
if mySal < v_sal then
doInsert;
else
-- We want to display a message here, when mySal > v_sal
end if;
end;
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Answer 1

I did something similar but wasn't using a stored procedure. Couldn't you set a flag variable once you know you're not doing the insert and in the "before displaying the form" section put an IF to check if your flag was set, and if so do an HTP.Print('You are overpaid buddy!');
Then just reset your flag.