I added few comboboxes to the form "Item Card".
The selected values of the comboboxes must be depended on ItemCode.
So I need to get ItemCode when the item data is loading to the form (OK_MODE, UPDATE_MODE).
Which event (and how?) can I use to catch field value (in my case, item code) after the form is filled?
Its partly possible to catch the event you are speaking of.
There are several ways to open the itemCard form: By the menu, when navigating using the navigate arrows, from link arrows etc.
It is NOT possible to catch all of theese events, which meens you cannot make you addon works in all cases.
This is a general problem with all SBO system forms, and it have been repported to SAP.
I hope you find another way around.