allow incoming ftp from certain IP’s only….with pix 515e

I want to block all ftp traffic coming in on my external interface, other than from 2 certain IP’s. I also use this interface for VPN so I don’t want to block all protocols on the interface.I need some help on what the exact acl commands are to block ftp other than from the two trusted sources and save the config. Pix v 6.3 (4)Any help would be greatly appreciated.