OnDocFormSave.php

<?php

switch ($modx->event->name) {

	case 'OnDocFormSave':
		if (!$product = $modx->getObject('msProduct', $resource->get('id'))) {
			return '';
		}

		/** @var currencyrate $currencyrate */
		if (!$currencyrate = $modx->getService('currencyrate', 'currencyrate', $modx->getOption('currencyrate_core_path', null, $modx->getOption('core_path') . 'components/currencyrate/') . 'model/currencyrate/', array())) {
			return 'Could not load currencyrate class!';
		}

		$valutes = array(
			'price_eur' => 'EUR',
			'price_usd' => 'USD'
		);

		foreach ($valutes as $field => $valute) {
			if (!$valute = $modx->getObject('CRlist', array('charcode' => $valute, 'active' => 1))) {
				continue;
			}
			$valuerate = $valute->get('valuerate');
			if (empty($valuerate)) {
				continue;
			}

			$valutePrice = $product->get($field);
			if (empty($valutePrice) OR ( $valutePrice == '0.00')) {
				continue;
			}

			$price = $valutePrice * $valuerate;
			$product->set('price', $price);
			$product->save();
		}

		break;
}