Please refer to this link , is a multiple select box to select sub-activity base on what is picked in main-activity, its working pretty well now.
Based on change request, I want to make the action to show only the optgroup in sub-activity when it being select, means when you select main-activity option 1 and 2
, sub-activity
are show optgroup for 1 and 2
, the rest are hide and not visible, please advise, thanks.