begin
var_cdo_content := :new.cdo_content;
loop
if instr(var_cdo_content,str_flag1) > 0 then
var_start := instr(var_cdo_content,str_flag1);
elsif instr(var_cdo_content,str_flag2) > 0 then
var_start := instr(var_cdo_content,str_flag2);
end if;
if var_start > 0 then
var_end := instr(var_cdo_content,str_flag3);
end if;
exit when (var_start=0 or var_end=0);
if var_start > 0 and var_end > 0 then
str := substr(var_cdo_content,var_start,var_end-var_start+length(str_flag3));
end if;
var_cdo_content := replace(var_cdo_content,str);
end loop;
:new.cdo_content:=var_cdo_content;