Asad,
Yeah I am aware of this custom action and I have done it for one of my BO and in that Bo with the help of code it is working fine for me. Now I am talking about this. In our Owl as shown you can find the menu called toolbar in the properties window after selecting the region as shown.
In this if you try to configure it then you will have a window with many action buttons as shown. These are defaultly created when you BO is populated with the screens (Create Screens) and in this the buttons "New Edit and Export" are configured with default out ports automatically. So no need of doing anything to them. If in case you are looking for some other button lets say in my case delete button then do in following way...
When you try for configuring the toolbar in the properties window the following window will open with following options
In this from the Available you select the needed action button and press the arrow mark button to make this to be available in your current region, it means current region will resemble your current OWL screen. So I have selected the delete button and moved it to the current region. Now a delete button will be available on the screen and to this an event has to configured lets say in our case it has to delete the row in the list so used the following operation accordingly for a event handler and this delete button is configured with this event handler.
Now this should work but the delete button is in grayed out mode on the screen. The above process is another way of getting the delete action button with out using any kind of custom code/custom action. Hope you are now knowing about this second method 
but I have to see who is going to make me know what the mistake I had done in doing this.
Regards..
Hanu K