function Form1_Validator(theForm)
{

var alertsay = ""; // define for long lines
// alertsay is not necessary for your code,
// but I need to break my lines in multiple lines
// so the code won't extend off the edge of the page

// require at least one radio button be selected
var radioSelected = false;

if(theForm.option.length) {
for (i = 0;  i < theForm.option.length;  i++)
{
if (theForm.option[i].checked)
radioSelected = true;
}
if (!radioSelected )
{
alert("Por favor elija el nivel del curso");
return (false);
} } else
// because this is a sample page, don't allow to exit to the post action
// comes in handy when you are testing the form validations and don't
// wish to exit the page
//alertsay = "All Validations have succeeded. "
//alertsay = alertsay + "This is just a test page. There is no submission page."
//alert(alertsay);
return (true);
// replace the above with return(true); if you have a valid form to submit to
}