Drag drop and collection Select box

Hello all,
I am new to rails development. I have a listbox with multi select
option. The box is populated with a list of contacts. I am trying to
implement drag drop functionality. But for some reason I am not able to
select the item. I think i am making a mistake assigning the correct id
to the draggable_element

i have the following code.

<%=select_tag(“lstcontacts”,options_from_collection_for_select(@contacts,:id,:name),
:multiple => true, :size => 10 ) %>

<%= draggable_element(“lstcontacts”, :revert => true) %> . How do I
specify the id correctly? Can someone help me with this please. Also if
I want to select multiple items. Can that be done?

Thanks
Kiran