Magento Add fee on grand-total depending about payment gateway user selcted -

I need to add additional charges and the total fee charge gateway depends on the user if the user's payment method is of 1 fee The selection is $ 3 and so on .... I'm able to add fees to the Grand Total with the help of "sales_quote_collect_totals_after" supervisor.

Now I need to get the current payment gateway, so I will charge that user.

Thanks in advance