Javascript on load event error

var ctrlPrice = Runner.getControl(pageid, 'UnitPrice');
var ctrlQuantity = Runner.getControl(pageid, 'Quantity');
var ctrlTotal = Runner.getControl(pageid, 'packing');
function func() {
var ctrlTotal =ctrlPrice*ctrlQuantity;

ctrlTotal.on('keyup', func);
};
this is what i wrote but it is not working plz give me a correct and i also need to get alert message on the scrren of the total value plzzzzzzz supply correct alert message.
plzz give me sample code for this