I think this is what you need. I did not test it though.
var ignoreEvents = false;
function nodeEventHandler(treeview, node, eventType)
{
if (ignoreEvents) return;
ignoreEvents = true;
if (eventType == \"checked\") {
var checkedNodes = treeview.findAll(function(matchNode){ return matchNode.getChecked(); });
for(var i = 0; i < checkedNodes.length; i++)
{
if (checkedNodes[i] != node)
checkedNodes[i].setChecked(false);
}
}
ignoreEvents = false;
}