jQuery AutoCompleteTextBox with dynamic options

I have 2 AutoCompleteTextBoxes in my ASP.Net page. I need the 2nd textbox to get the value from the first box and assign it as one of the options to pull up the list. Client-side only.

$("#txtBox1").AutoCompleteTextBox({ type: "val1", minLength: "3", userid: '1234' });

$("#txtBox2").AutoCompleteTextBox({ type: "val2", minLength: "3", userid: '1234', 
        cc: $('#txtBox1').on('autocompletechange change', function () {
        //alert(this.value);
        return this.value;
    }) 
});

So, cc needs to get the value selected in txtBox1 and popup the list of values returned from the sql proc. I tried text() and val() after the function. The alert works and has the value. But the end result is '' getting sent to the AJAX. I even tried a knockout variable attached to a label and tried

<%=lblTxtBox1.Text%>

But it's not working. All I need is for the options going to the AJAX call to look like

cc: 'abcd'

Any help is appreciated. Thanks much.

RESOLVED!

I needed a keyup event. I also indexed the table on the search fields as the response was very slow.

var cc = '';

$('#txtBox1').on('focusout', function() {
  cc = this.value.toString();
});

var cc = this.value; // this will also work

$("#txtBox2").on('keyup', function() {
    $("#txtBox2").AutoCompleteTextBox({ type: "type2", minLength: "3", userid: '1234', ccode: '' + cc + '' });        
});