Limit jQueryUI Slider to go below an amount

I need to "freeze" the slider if user selects something from the checkboxes. My code is as follows:

$('#slider').slider({
            range: 'min',
            value: 20,
            min: 0,
            max: 500,
            slide: function(event, ui) {
                $('input#amount').val('$' + ui.value);
            }
        });
$('div.checkboxes').children('p').children('input').each(function() {
    $(this).change(function() {
        var amount = $(this).attr('data-amount'),
            curr = $('input#amount').val().replace('$',''),
            newPrice = parseFloat(curr)+parseFloat(amount),
            oldPrice = parseFloat(curr)-parseFloat(amount);

        if($(this).is(':checked')) {
            $('#slider').slider({
                'value': newPrice
            });
            $('input#amount').val('$' + newPrice);
        } else {
            $('#slider').slider({
                'value': oldPrice
            });
            $('input#amount').val('$' + oldPrice);
        }
    })
})

As you can see, it slides to some range when one or more checkboxes are checked. But my problem is - when user clicks on each checkbox and then manually slide the price down. What can I do to prevent this?

The only way I know is to check the value in the slide function and if it's not respect you limit return false from the function itself.

In my example I set a globally scoped variable prizeLimit from a button (but I can be set everywhere) and in the slider slide event I check the variable.

Code:

var prizeLimit = 0;

$(document).ready(function () {

    $('#amount').val('$20');

    $('#slider').slider({
        range: 'min',
        value: 20,
        min: 0,
        max: 500,
        slide: function (event, ui) {
            if (ui.value < prizeLimit) return false;

            $('#amount').val('$' + ui.value);
        }
    });

    $('#setPrizeFree').click(function () {
        prizeLimit = 0
    });

    $('#setPrizeMin').click(function () {
        prizeLimit = 158
        $('#slider').slider({
            'value': 158
        });
        $('input#amount').val('$158');
    });

});

Demo : http://jsfiddle.net/IrvinDominin/3bCzb/