I opened a new column in “cscart_product_prices” table in database. Named custom_price.
in app\addons\my_addon\controllers\backend\products.post.php I added the codes below.
<br />
if ($mode == 'update') {<br />
<br />
$product_data = Registry::get('view')->getTemplateVars('product_data');<br />
$data = db_get_row("SELECT custom_price FROM ?:product_prices WHERE product_id = ?i", $product_data['product_id']);<br />
$product_data['custom_price'] = $data['custom_price'];<br />
Registry::get('view')->assign('product_data', $product_data);<br />
}<br />
```<br />
<br />
I can pass the value to the themplate.<br />
<br />
design\backend\templates\addons\my_addon\hooks\products\update_detailed_images.pre.tpl file:<br />
<br />
```php
<br />
<input type="text" name="product_data[custom_price]" id="elm_price_price" size="10" value="{$product_data.custom_price}" class="input-long" /><br />
```<br />
<br />
I couldn't save variable that I passed to products update page. How to save new data into database when pressing update button in product page?