Hi Ben,
Thanks for all these information. Sorry that I didn't mentioned that I change the action of "Vendor's dropdown", so it does not save Bill when vendor is changed. I also tried your suggestion like:
1. in "Select PO..." button, I add an action to call default "Save" button as the first action. (Right before condition warning action.)
2. I tried to test it again, it is a bit better, but still the next "Condition warning" (to check screen's active RecordID) is triggered for no active screen RecordID sometimes.
You mentioned that a "delay" is long enough by calling a button's action, it sounds like active RecordID is not generated along with "Save all sections" immediately?
I need to alter the origial screen because it creates several empty Bills in our system, and that is caused by a Bill is created, but users don't want to add Bill items or no Bill items are available. So, in our real implementation, we do change default Bill screen and PO_OpenPO screen a lot, so, the Bill is actually created when users select some items and save. However, it does not work as expected, so we go back to do more test on default screen (calling save all sections from action to get active screen RecordID), and see how it goes, and, this is what we have now.
Thanks again.
Alex