Tabular Form Checked Value Pas as a parameter to Popupwindow in Oracle APEX

[SRISRISIVA]

I got a requirement. i have a tabular form with some records, for example i have a department table in a tabular form, if i check first record that means department 10 and then if i click any button we need to show the list of employees whose department is 10.

I tried this scenario like... i created two buttons "Pick_record" and "Show_employees",for Pick_records i created a process and the code is

DECLARE
 vRow BINARY_INTEGER;
 BEGIN
 :P4_HIDDEN_ITEM := NULL;
 :P4_SELECTED_RECORD := NULL; 
 :P8_BOM_ITEM := NULL;
 FOR i IN 1 .. apex_application.g_f01.COUNT
 LOOP
  vRow := apex_application.g_f01(i);
  :P4_SELECTED_ITEM:= apex_application.g_f02 (vRow);
 END LOOP;
:P4_HIDDEN_ITEM := :P4_SELECTED_ITEM;
:P8_BOM_ITEM:= :P4_SELECTED_ITEM;
END;

Above code will assign the tabular form checked value to the apex page items. Those items will be passed to popup window.
So if i click pick_record button tabular form checked value assigning to page items after that if i click show_employees button then only popup window opening with tabular form checked value as a parameter.

But actually i don't want to click 2 buttons.I just check the any row in tabular form records and then i click show_employees button. Then popup window will open with tabular form checked value as a parameter.