Can I "catch" a click on a sortable column header of a report?

Question

Hi,
I have a report.
Most columns are made sortable: users can click on them to sort.
I notice that when clicked only page-rendering executes (i.e. not page processing).
Here is the question.
I need to call some custom PL/SQL when the user clicks on a sortable column header. This PL/SQL could executes in the before header (it needs to fire before the page re-executes the query).
The PL/SQL needs to know which column was clicked on: how can I determine this?
Can I access the url (example below)? I see that it shows which column was clicked.
https://dev.centraal.boekhuis.nl:4443/pls/apex/f?p=100:3:145900176972409:fsp_sort_4::RP&fsp_region_id=1562722058676533
Thanks,
Toon

Answer 1

That would order the report by C1 when I click C2, which isn't what I want. I want to preserve the order of C1 (whether that's ascending or descending) and then have C2 ascend or descend for each set of values in C1.
If I can't set the Order By then I'll need something like this as my query. The "last_col1_order" and "this_col2_order" would be items, set according to the last few values of Request. It's horrible, but it gets the job done. This would be so easy in forms!
WITH data AS (
  select level col from dual connect by level < 6)
SELECT
  col1,
  col2,
  lpad(case last_col1_order
         when decode(this_col2_order,'asc','asc','desc') then col1
         else col1_desc end,20,'#') ||
    lpad(col2,20,'#') col2_sort
FROM (
  SELECT
    col1,
    col2,
    (max(col1) over(partition by 1))-(dense_rank() over(order by col1)) col1_desc,
    'asc' last_col1_order,
    'desc' this_col2_order
  FROM (
    SELECT a.col col1, b.col col2
    FROM data a, data b
order by col2_sort desc