<script type="text/javascript">
 
 
 
    // This javascript sets the default value of a lookup field identified
 
    // by <<FIELD DISPLAY NAME>> to the value stored in the querysting variable
 
    // identified by <<QUERYSTRING VARIABLE NAME>>
 
 
 
 
 
    // Customize this javascript by replacing <<FIELD DISPLAY NAME>> and
 
    // <<QUERYSTRING VARIABLE NAME>> with appropriate values.
 
    // Then just paste it into NewForm.aspx inside PlaceHolderMain
 
 
 
    _spBodyOnLoadFunctionNames.push("fillDefaultValues");
 
 
 
    function fillDefaultValues() {
 
      var qs = location.search.substring(1, location.search.length);
 
      var args = qs.split("&");
 
      var vals = new Object();
 
      for (var i=0; i < args.length; i++) {
 
        var nameVal = args[i].split("=");
 
        var temp = unescape(nameVal[1]).split('+');
 
        nameVal[1] = temp.join(' ');
 
        vals[nameVal[0]] = nameVal[1];
 
      } 
 
      setLookupFromFieldName("<<FIELD DISPLAY NAME>>", vals["<<QUERYSTRING VARIABLE NAME>>"]);
 
    }
 
 
 
    function setLookupFromFieldName(fieldName, value) {
 
      if (value == undefined) return;
 
      var theSelect = getTagFromIdentifierAndTitle("select","Lookup",fieldName);
 
 
 
    // if theSelect is null, it means that the target list has more than
 
    // 20 items, and the Lookup is being rendered with an input element
 
 
 
      if (theSelect == null) {
 
        var theInput = getTagFromIdentifierAndTitle("input","",fieldName);
 
        ShowDropdown(theInput.id); //this function is provided by SharePoint
 
        var opt=document.getElementById(theInput.opt);
 
        setSelectedOption(opt, value);
 
        OptLoseFocus(opt); //this function is provided by SharePoint
 
      } else {
 
        setSelectedOption(theSelect, value);
 
      }
 
    }
 
 
 
    function setSelectedOption(select, value) {
 
      var opts = select.options;
 
      var l = opts.length;
 
      if (select == null) return;
 
      for (var i=0; i < l; i++) {
 
        if (opts[i].value == value) {
 
          select.selectedIndex = i;
 
          return true;
 
        }
 
      }
 
      return false;
 
    }
 
 
 
    function getTagFromIdentifierAndTitle(tagName, identifier, title) {
 
      var len = identifier.length;
 
      var tags = document.getElementsByTagName(tagName);
 
      for (var i=0; i < tags.length; i++) {
 
        var tempString = tags[i].id;
 
        if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) {
 
          return tags[i];
 
        }
 
      }
 
      return null;
 
    }
 
    </script>