Add and Remove List items from one Listbox to another Listbox Using Javascirpt

function _ADD_REMOVE(sobjRemoveFrom,sobjAddTo,bAll) //For List Box Control
        {
            var sPreFix="ctl00_ChildMaster_"


              var iCurrentIndex = 0;
              var objRemoveFrom = document.getElementById(sPreFix+sobjRemoveFrom);
              var objAddTo = document.getElementById(sPreFix+sobjAddTo);
              if(bAll==true)
              {
                  for(var i = 0; i < objRemoveFrom.length;i++)
                  {
                      iCurrentIndex = objAddTo.length;
                      objAddTo.options[iCurrentIndex] = new Option();
                        objAddTo.options[iCurrentIndex].text = objRemoveFrom.options[i].text;
                        objAddTo.options[iCurrentIndex].value = objRemoveFrom.options[i].value;
                  }
                  for(var j = 0; j < objRemoveFrom.length;j++)
                  {
                      objRemoveFrom.options[j--]=null;
                  }
              }
              else
              {
                  for(var i = 0; i < objRemoveFrom.length;i++)
                  {
                      if(objRemoveFrom.options[i].selected==true)
                      {
                          iCurrentIndex = objAddTo.length;
                          objAddTo.options[iCurrentIndex] = new Option();
                            objAddTo.options[iCurrentIndex].text = objRemoveFrom.options[i].text;
                            objAddTo.options[iCurrentIndex].value = objRemoveFrom.options[i].value;
                        }
                  }
                  for(var i = 0; i < objRemoveFrom.length;i++)
                  {
                      if(objRemoveFrom.options[i].selected==true)
                      {
                          objRemoveFrom.options[i--]=null;
                        }
                  }
              }
        }




<input type="button" id="btnSecAddAll" name="btnSec" value=">>" class="field" onclick="_ADD_REMOVE('lstSkillLst','lstSelectedSkill',true);" style="width:50px" /><br /><br />
                                             <input type="button" id="btnSecAdd" name="btnSec" value=">" class="field" onclick="_ADD_REMOVE('lstSkillLst','lstSelectedSkill',false);" style="width:50px" /><br /><br />
                                         <input type="button" id="btnSecRem" name="btnSec" value="<" class="field" onclick="_ADD_REMOVE('lstSelectedSkill','lstSkillLst',false);" style="width:50px" /><br /><br />
                                         <input type="button" id="btnSecRemAll" name="btnSec" value="<<" class="field" onclick="_ADD_REMOVE('lstSelectedSkill','lstSkillLst',true);" style="width:50px" />