I have a form that I need to auto submit when a user has clicked three of the possible 'x' number of checkboxes. I know I will use the onclick attribute to call a function to check to see how many are filled in, but I'm unclear as to the syntax to refer to the checkboxes in my attempt to count how many are checked. I guess I should post the code for the form for reference:

<form method="post" action="/calc.php" name="processform">
<input type="hidden" name="compare" value="true" />
Enter your average ticket price: <input type="text" name="aveticket" width="10" />
Enter your average number of transactions per month <input type="text" name="numtickets" width="10" />

<input type="checkbox" name="processors[]" value="1" onclick="someFunction">JNA Web Design</input>
<input type="checkbox" name="processors[]" value="2" onclick="someFunction">Paypal</input>
<input type="checkbox" name="processors[]" value="3" onclick="someFunction">WorldPay</input>
<input type="checkbox" name="processors[]" value="4" onclick="someFunction">2CheckOut</input>
<input type="checkbox" name="processors[]" value="5" onclick="someFunction">PaySystems Plan A</input>
<input type="checkbox" name="processors[]" value="6" onclick="someFunction">PaySystems Plan B</input>

<input type="submit" value="Compare Programs" />