How do I make jQuery code execute when a checkbox is checked programatically somewhere else?

I have a HTML form with a dropdown box (<select id="state"> ... </select> tag). I have a checkbox next to it (<input type="checkbox" id="not-from-US" />).

The HTML dropdown item has a list of all United States stas (MO,TX,AL,etc.). But if the user is not from the United States, he/she checks the "Not from US" checkbox. Now in jQuery, I have programmed the checkbox (via .change()) to generate an additional field for selecting a country when the checkbox is checked. It also makes the dropdown select the "N/A" option.

I also programmed my form so that if the user selects "N/A" from the "States" dropdown menu, the "Not from US" checkbox gets checked. But how do I link the two events together? When the checkbox is programatically checked, the anonymous function for when the checkbox is checked does not fire.

How can I fix this?

Edit: Sorry, I forgot to attach the sample code. Here it is:

------------------index.php------------------

<form action="index.php" method="post">
    <select id="state">
       <option value="None">None</option>
       <option selected="true" value="AL">AL</option> 
       <option value="AK">AK</option> 
       <option value="AZ">AZ</option>
       <!--etc.-->
    </select>
    <input type="checkbox" id="not-from-usa" name="not-from-usa" />
</form>

------------------main.js------------------

$(document).ready(function(){
    $('#state').change(function(){
        if ($(this).val() == "None") {
            $('#not-from-usa').attr('checked','checked');    // This is the important bit.
            // So now the #not-from-usa checkbox is checked. So the code below should execute, right?
        } else {
            $('#not-from-usa).removeAttr开发者_JS百科('checked');
        }
    });

    $('#not-from-usa').change(function(){
        if($(this).attr('checked')) {
            // Create an input element that the user can enter a country
            // Code omitted for clarity.

            // The code in here should execute once the checkbox is checked or unchecked.
            $('#state').val("None");    // Set the dropdown to the "None" selection
        } else {
            // Remove the extra input element that lets the user enter a country.
        }
    });
});

Use the function checkbox.click() rather then setting checkbox.checked = true;

I have edited this post.

Well the http://api.jquery.com/trigger/ gives you what you want.

With trigger you dispatch the event. So just add one $("checkbox").trigger('click'); That should do the trick.

In pure javascript,you can use the .checked attribute:

if(document.getElementById("not-from-US").checked) {
   //checked, do something
} else {
   //not checked, do something.. 
}