Thanks everyone, I got the answer. Instead of using Rules, I created a "custom feeds module."

Steps:

1. Create a folder named "custom_feeds"
2. Create two files, one is "custom_feeds.info", another is "custom_feeds.module"
3. Add following information in the .info file:
<code>
; $Id: $
name = custom feeds module
description =custom feeds module
core = 7.x
package = Feeds
dependencies[] = feeds</code>

4. Add following code in the .module file inside '<'?php?>':
<code>
function custom_feeds_feeds_presave(FeedsSource $source, $entity, $item) {
	// check that this is fired only for the importer being used
	if($source->importer->id=='recommended_product_import'){
    // "equivalent" is the column name in excel sheet
		if(!strcmp($item['equivalent'],"")){
			$entity->feeds_item->skip = TRUE;
        }
      }
}
</code>