function CallbackPopulatedTree (varName, ajaxFunction, expandHtml, collapseHtml, loadingMarkup)
{
	this._variableName = varName;
	this._ajaxFunction = ajaxFunction;
	this._expandHtml = expandHtml;
	this._collapseHtml = collapseHtml;
	
	this._loadingElement = null;
	this._loadingPageId = null;

    this._expand = function(pageId, element)
    {
        if (element.parentNode.parentNode.childNodes.length == 2)
        {
            element.parentNode.parentNode.childNodes[1].style.display = 'block';
            element.onclick = new Function(this._variableName + '._collapse(\'' + pageId + '\', this); return false');
            element.innerHTML = this._collapseHtml;
        }
        else if (!this._isProcessingCallback())
        {
            var le = document.createElement('div');
            le.innerHTML = loadingMarkup;
            element.parentNode.parentNode.appendChild(le);
            element.onclick = new Function('return false');
            this._loadingElement = element;
            this._loadingPageId = pageId;

            this._ajaxFunction('getchildren', pageId, new Function('result', 'window.' + this._variableName + '._expandCallback(result);'), new Function('window.' + this._variableName + '._resetCallback();'));
        }
    }

    this._expandCallback = function(html) 
    {
    	if (html) 
    	{
    		if (this._loadingElement && this._loadingPageId) 
    		{
    			var element = this._loadingElement;
    			var pageId = this._loadingPageId;

    			element.parentNode.parentNode.childNodes[1].innerHTML = html;
    			element.parentNode.parentNode.childNodes[1].style.display = 'block';
    			element.onclick = new Function(this._variableName + '._collapse(\'' + pageId + '\', this); return false');
    			element.innerHTML = this._collapseHtml;
    		}
    	}
    	
    	this._resetCallback();
    }
    
    this._collapse = function(pageId, element)
    {
        if (element.parentNode.parentNode.childNodes.length == 2)
        {
            element.parentNode.parentNode.childNodes[1].style.display = 'none';
            element.onclick = new Function(this._variableName + '._expand(\'' + pageId + '\', this); return false');
            element.innerHTML = this._expandHtml;
        }
    }
    
    this._resetCallback = function()
    {
        this._loadingPageId = null;
        this._loadingElement = null;
    }
    
    this._isProcessingCallback = function()
    {
        return this._loadingPageId != null || this._loadingElement != null;
    }
}