Authorization code - another syntax issue

Question

Hi people,
If I want to create an Authorization Scheme on the presence of certain text within a string but (as usual) my syntax is letting me down,
I have a global variable present - and if the first two letters of the global variable are 'NT' then the user is allowed to see the page.
But I am failing to specify this in the Authorization Scheme setting.
If I had the option of PL/SQL code I would put...
substr('&F999_MYGLOBAL..', 1, 2) = 'NT';
...but this is not an option.
Examples that I have tried.
Vaule in Expression1 Equals Expression2 (where Expression 1 = substr('&F999_MYGLOBAL.', 1, 2) and Expression2 = 'NT'
And other combinations of the above.
Help?

Answer 1

Neil,
I have a global variable present...We don't have local and global scope in Application Express - all items are visible from everywhwere. But I know what you mean, you have an application item.
If I had the option of PL/SQL code I would put...Ah, but you do, a PL/SQL Function returning Boolean authorization scheme:
if substr(:F999_MYGLOBAL, 1, 2) = 'NT' then
  return true;
else
  return false;
end if;Scott