Custom field Rules implementaion I added new "Markup" field into commerce_product table using custom module. Now I need to create a rule to calculate (sell_price=prod_price*markup), but I can't acccess Markup field throught Rules selectors. Is there a UI , or what hooks should I implement to solve that problem?
Here is complete comm_markup module code:

function comm_markup_schema_alter(&amp;$schema) {
  $schema['commerce_product']['fields']['markup'] = array(
    'type' =&gt; 'float',
    'not null' =&gt; TRUE,
    'default' =&gt; 1,
    'description' =&gt; 'Price markup field',
  );
}

function comm_markup_install() {
  $schema = drupal_get_schema('commerce_product');
  db_add_field('commerce_product', 'markup', $schema['fields']['markup']);
}

function comm_markup_entity_property_info_alter(&amp;$info) {
  $properties = &amp;$info['commerce_product']['properties'];
  $properties['markup'] = array(
    'label' =&gt; t('Price markup'),
    'type' =&gt; 'decimal',
    'description' =&gt; 'Gross price multiplier (defines profit amount).',
    'schema field' =&gt; 'markup',
    'getter callback' =&gt; 'entity_property_verbatim_get',
    'setter callback' =&gt; 'entity_property_verbatim_set',
  );
}

function comm_markup_views_data_alter(&amp;$data) {
  $data['commerce_product']['markup'] = array(
    'title' =&gt; t('Price markup field'),
    'help' =&gt; t('Multiplier. Adds profit to the gross price.'),
    'field' =&gt; array(
      'handler' =&gt; 'views_handler_field_numeric',
      'click sortable' =&gt; TRUE,
    ),
    'filter' =&gt; array(
      'handler' =&gt; 'views_handler_filter_numeric',
    ),
    'sort' =&gt; array(
      'handler' =&gt; 'views_handler_sort',
    ),
  );
}
Simple UI solution:

Add a condition of "Data Comparison"
Data selector - commerce-line-item:type
Value equals - "Modification" (or whatever your custom line item type is called)

Now when you add a condition that checks for a field, all the fields on that custom line item type should appear. Example, "Data value is empty - commerce-line-item:custom-field".
Thanks to trevorkjorlien comment at Drupal.org