a javascript question.

i have three radio buttons and I want to, on form submit, verify what one has been choose.

I am trying this:
var strURL=document.frmEvent.txtURL.value;
var optionButtonSelected=document.frmEvent.inpURL.checked;
alert(optionButtonSelected);


this is inside the function called by the submit button.

i have the names correct.
the form is called frmEvent and there is a text field called txtURL and the radio buttons are all called inpURL.

as you can see i have an alert to get the value from the checked radio but it comes back 'undifined'

so what am i doing wrong?
any suggestions are welcome,
if you need more information , just ask.

thanks