Help with AJAX

Hi,

I'm using some custom variant fields in my product reader, I have a drop down box and I need the price to update when the field is changed much like the default options fields that Isotope produces.

How do I 'register' the fields so that they send an AJAX request when they are changed?

I see this line in IsotopeProduct.php has something to do with it:

Code:

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$GLOBALS['TL_MOOTOOLS'][] = $startScript."\nnew {$this->ajaxClass}('{$objModule->id}', '" . ($this->pid ? $this->pid : $this->id) . "', '{$this->formSubmit}', ['ctrl_" . implode("_".$this->formSubmit."', 'ctrl_", $arrAjaxOptions) . "_".$this->formSubmit."'], {language: '{$GLOBALS['TL_LANGUAGE']}', page: {$objPage->id}, loadMessage:'" . specialchars($GLOBALS['ISO_LANG']['MSC']['loadingProductData']) . "'});\n".$endScript;

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Can someone explain how the AJAX call should work - from request to response?

Thank you!