Coding for list item in Oracle developer

Hi,

I have got two list items .i want to add list elements from one list item to another.i have got a button between these two list items to add the elements.
please do help me and tell me what coding has to be written in the When_Button_pressed trigger of the button.The list items are list1 and list2.
One condition is after every move the control must be placed in the first element of list1 and last element of list2.