Magento

Hi,
I cannot find answer to this. How do I skip payment step if it makes no sense (i.e. store pickup or pay upon delivery)? If it is not possible from admin panel, what file should I hack on? Skipping payment step is basically dependent on “Shipping method”. I have found, in source, shipping ids that would allow for payment skipping but I do not know what to do with it.

Thank you,
Radek.