window.onerror = myError;

function myError()
{
	return true;
}

function myTest(x,y,test,result)
{
	if(test.value == "") {
		result.value = "(type an operator above)"
	}
	else {
		result.value = "(error)";
		result.value = eval("window.onerror = myError;var x = " + x.value + "; var y = " + y.value + "; x " + test.value + " y;");
	}
}