Adding multiline text to a listbox and how to pass line by line in a session to another page?

I am trying to add text to list box using the javascript code below. I have a search box above the list box that a user can select a name after searching and then it adds the record to the textbox. My goal is to have each record on a separate line after it is selected from my search box. It works for a multiline textbox but if I use a listbox instead it does not work? There are no errors.
Also, there could be any number of results rows populated in the listbox, how would I pass these values to another page? Would a session work when I need to read the listbox text line by line for my insert statement on the final page? Thanks in advance for any suggestions.
<script language="javascript" type="text/javascript"> function getSelected(source, eventArgs) { var s = $get("<%=NameTextBox.ClientID %>").value; document.getElementById('<%= NPTextbox.ClientID %>').value += s.su ...