alert(RowIndex) on Keydown 'Enter'

Can anyone explain how you make an alertbox displaying the rowindex then pressing the Enter key on the selected row?

Found out my self.

Here it goes for those of you with the same problem.

var defaultEventHandler = obj.getEvent("onkeydown");  
obj.setEvent("onkeydown", function(e){ 
if(event.keyCode==13){
var rowid = obj.getSelectedRows()
alert(rowid);
event.returnValue = false;  
 }
else{ 
 defaultEventHandler.call(this, event);  
 event.returnValue = false;  
 } 
 } );