image load check not working

Hi Everyone,

I need help with my code. I am trying to display the image based on if it is available or not.
In my javascript function, It always displays def.gif image but no flag.gif image.
Do i have to do different to check the image load?

I want to display in IE 8 browser.

Thanks,
tdhumal

Here is my code:

My xslt code where the arguments are passed.
*********************************************************************
<xsl:for-each select="TEST/RECORD/OUTPUT">
              <xsl:sort select="REC" data-type="number" order="descending"/>
              <xsl:sort select="FLAG" data-type="text" order="ascending"/>
              <script type="text/javascript">
                WriteOutFiles("<xsl:value-of select="REC"/>",
                             "<xsl:value-of select="RECSEL"/>",
                             "<xsl:value-of select="RECBY"/>",
                             "<xsl:value-of select="RECWR"/>",
                             "<xsl:value-of select="FILEN"/>",
                             "<xsl:value-of select="FLAG"/>")
              </script>
            </xsl:for-each>
*******************************************************************

My Javascript where I am trying to display "FLAG"

*******************************************************************
function WriteOutFiles(rec, recSel, recB, recW, out, Flag)
{
        var outAry;
       var checkImg = null;
      var imgsrc = '/dir/img/' + Flag + '.gif';
      var img = new Image();
      img.onload = function (evt) {
            checkImg = true;
        }
      img.onerror = function (evt) {
            checkImg = false;
        }
        img.src = imgsrc;
      var out = 'output' + parseInt(outAry);
      document.write('<table width="876" border="0" cellpadding="0" cellspacing="1" class="tablesorter" id="' + out + '">');
              document.write('<thead>');
                document.write('<tr>');
                  document.write('<th width="57" scope="col">');
                 if(checkImg == true)
                  document.write('<img src="/dir/img/' + Flag + '.gif">');
                  else if(checkImg == null)
                  document.write('<img src="/dir/img/def.gif">');