Thank you dear Rob.. Actually i have already take a look on the knowledgebase.. The issues i have with this code are:   
1) I need to check my SKU field to match the products when updating from form A to Form B... But in the example it's checking the user id instead of product SKU..  
2) In this example it addresses two specific fields to get data from form A and write data to form B. Since i have several repeaters in form A how can i address each repeater sections SKU field and stock quantity fileds?    

SAMPLE CODE

add_action('frm_after_create_entry', 'link_fields', 30, 2); add_action('frm_after_update_entry', 'link_fields', 10, 2);
function link_fields($entry_id, $form_id){
if($form_id == 113){//Change 113 to the ID of the first form
global $wpdb;
$first_field = $_POST['item_meta'][25]; //change 25 to the ID of the field in your first form
$user = $wpdb->get_var($wpdb->prepare("SELECT user_id FROM ". $wpdb->prefix ."frm_items WHERE id=%d", $entry_id));
$entry_ids = $wpdb->get_col("Select id from ". $wpdb->prefix ."frm_items where form_id='112' and user_id=". $user);//Change 112 to the ID of the second form
foreach ($entry_ids as $e)
$wpdb->update( $wpdb->prefix .'frm_item_metas', array('meta_value' => $first_field), array('item_id' => $e, 'field_id' => '6422'));//Change 6422 to the ID of the field to be updated automatically in your second form
}
}