Call of theme function to Custom Module

How to call theme function to my custom module ?

below function is working for only node.tpl.php not for custom module.

  print theme('hover_preview', $node, 'field_mycckfieldname', 'Thumbnail','BigImage');

I have my module having a list of all nodes, and i have added theme function in for loop to display hover effect. but its not working.

my code in custom module is,

$node = node_load($node->nid);

print theme('hover_preview', $node, 'field_product_image', 'productsearch_img','productsearch_img');

when i visit my page, it display only images there is no hover effect,i have also research and found that js and css are also not added in the page.

please help on this.