Magento – Price increments in layered navigation

to filter on a specific price range your category url looks something like http://domain.com/categoryurl?price=65-200. To accomplish this I would suggest creating a new template file that has a form with a minimal and maximal price input with a submit button that when clicked will create an url like previously mentioned.

Here is some untested code that might help you along.

In your local.xml add the following to add a new block under the left layered navigation.

<catalog_category_layered>
    <reference name="left">
        <block type="core/template" name="pricefilter" after="-" template="catalog/layer/pricefilter.phtml"/>
    </reference>
</catalog_category_layered>

The pricefilter.phtml would look something like this

<?php echo $this->__('From');?>: <input type="text" name="minvalue" id="pricefilter-minvalue" value=""/><br/>
<?php echo $this->__('To');?>: <input type="text" name="maxvalue" id="pricefilter-maxvalue" value=""/><br/>
<a href="#" id="pricefilter-submit"><?php echo $this->__('Filter');?></a>

<script type="text/javascript">
$('pricefilter-submit').observe('click',function(){
    var minvalue = $('pricefilter-minvalue').value;
    var maxvalue = $('pricefilter-maxvalue').value;

    var dest = window.location.href;
    dest += (window.location.href.indexOf('?') != -1) ? '&' : '?' ;
    dest += 'price=' + minvalue + '-' + maxvalue;

    window.location = dest;
});

Basically you need a way to remove some filters from the given categories from the admin panel. It can be done either by some improved layered navigation extension or just be using category layout updates.

Open the category edit page, switch to the "Custom Design" tab, and put the code in the "Custom Layout Update" field

<reference name="catalog.leftnav"> 
    <action method="unsetChild"><alias>shoes_size_filter</alias></action>
</reference>