function getAbsoluteTop(objectId) {
 // Get an object top position from the upper left viewport corner
 // Tested with relative and nested objects
 o = document.getElementById(objectId)
 oTop = o.offsetTop            // Get top position from the parent object
 while(o.offsetParent!=null) { // Parse the parent hierarchy up to the document element
  oParent = o.offsetParent  // Get parent object reference
  oTop += oParent.offsetTop // Add parent top position
  o = oParent
 }
 // Return top position
 return oTop
}

function setIframeHeight(IframeName, layerName){
	var pos = getAbsoluteTop(layerName);
	top.document.getElementById(IframeName).style.height = pos + 20 + 'px';
}