how to reload jsp page in SAP portal through htmlb

Hi Everyone,

   We have NW portal 7.3 and still using jsp pages for portal screens and I tried to find an event for <hbj:inputField> but since I could not find any event like onchange, onblur etc for inputfield I used the code below to trigger "onchange event". No matter what code I write to reload the current page I am on and I want keep all the values entered on current page after reloading the page, it does not work. Please see all the code I tried in  jsp page and also javascript function kostlchanged(). So to summarize, I want to display and populate some drop down on jsp page when some value in input field is changed. For this to work, I have to somehow reload the current page by keeping all values entered when value in <hbj:inputField> is changed. I did extensive research and spent 8 hours, no luck, that's why I am posting here. I would appreciate all your feedback.

<hbj:inputField

type="STRING"
       id="KOSTL"

required="TRUE"
                
size='<%= ISR.getSize("KOSTL") %>'

maxlength='<%= ISR.getSize("KOSTL") %>'

value='<%= ISR.getValue("KOSTL") %>'
                
jsObjectNeeded="true">
                
  <%
   KOSTL
   .setClientEventExt(
    com

    .sapportals

    .htmlb

    .enums

    .EventTrigger

    .ON_CHANGE,

    "kostlchanged()");
  %>
                                 
</hbj:inputField>

function kostlchanged() {

    //window.opener.location.reload();
    //window.opener.location.href = window.opener.location;
    //window.location.reload(true);
    //window.location = window.opener.location;
    //check;
    //location.reload(false);
    //window.location.href = location.reload();
    //document.myform.submit();
    //
    //window.submit();

   }

Thanks.

--Ravi