Edit Custom Fields Drop down

[samper19]

In the custom fields drop down list it displays the (in this case) Size with a price to add to the base price EG:  50mm +$3.00 or  10mm No Additional Charge. 
I want to remove the description and just show the size  EG:  50mm 

I can find where this drop down is rendered in the file "components/com_virtuemart/sublayouts/customfields.php" and is rendered on this line of code
if (!empty($field->display)){ ?>
<div class="product-field-display"><?php echo $field->display ?></div><?php
}

$field->display  : creates the drop down box but I can't find where this function is run so I can modify the dropdown content.

can someone please point me in the right direction

regards
Sam P