Apply class to highest value over seperate columns

I have some code that works already but I'd like to change my page design, in doing this the add class script doesn't work. Here's what I've got for the design:

<tr>
    <td>Item 1</td>
    <td>&pound;<?php echo $row1['item1']; ?></td>
    <td>&pound;<?php echo $row2['item1']; ?></td>
    <td>&pound;<?php echo $row3['item1']; ?></td>
    <td>&pound;<?php echo $row4['item1']; ?></td>
    <td>Item 2</td>
    <t开发者_开发问答d>&pound;<?php echo $row1['item2']; ?></td>
    <td>&pound;<?php echo $row2['item2']; ?></td>
    <td>&pound;<?php echo $row3['item2']; ?></td>
    <td>&pound;<?php echo $row4['item2']; ?></td>
    <td>Item 3</td>
    <td>&pound;<?php echo $row1['item3']; ?></td>
    <td>&pound;<?php echo $row2['item3']; ?></td>
    <td>&pound;<?php echo $row3['item3']; ?></td>
    <td>&pound;<?php echo $row4['item3']; ?></td>
</tr>

Here's the jQuery code I've got:

 <script type='text/javascript'>
  //<![CDATA[ 
  $(window).load(function(){
  (function($) {
    $.fn.max = function(callback) {
        var max = null,
            maxIndex = null;

        this.each(function() {
            var value = callback.call(this);
            if (+value === value) {
                if (!max || value > max) {
                    max = value;
                    maxIndex = $(this).index();
                }
            }

        });
        return max !== null ? this.eq(maxIndex) : $();
    };
}(jQuery));


$('tr').each(function() {
    $(this).children('td').max(function() {
        var value = +$(this).text().substr(1);
        if (!isNaN(value)) {
            return value;
        }
    }).addClass('green bold');
});
  });
  //]]> 
  </script>

This works but only for each tr, meaning it highlights the highest value in each row, where as I need to it to highlight the highest value through each group (item 1, 2 and 3).

Can the code be changed for this to work?

Try looping through the TDs without first looping through the TRs:

$('table').find('td').max(function() {
    var value = +$(this).text().substr(1);
    if (!isNaN(value)) {
        return value;
    }
}).addClass('green bold');