var fopen = new Image();
var fclose = new Image();
fclose.src="/Graphics/Main/plus.gif";
fopen.src="/Graphics/Main/minus.gif";

function lnEC(theID){
  var theDiv=document.getElementById('div'+theID);
  var theImg=document.getElementById('img'+theID);
  if (theDiv.style.display=='none') { // hit +
    theDiv.style.display='';
    theImg.src=fopen.src;
  } else { // hit -
    theDiv.style.display='none';
    theImg.src=fclose.src;
  }
}