How do I control my volume from my interface only?

[william.bond55]

Hey, I no this isn't the best area to post this, but its the best I could find. When I first had my interface set up with pro tools my mac would only let me change the volume on the interface itself. Ive recently got another interface and am running them together optically. I was messing about trying to get them to work and I've changed something so that I can change the volume on my mac and my interface. I no you might think its pathetic but its actually making some sort of difference to the output of my monitors and I want to change back so I can only change the volume on my firewire interface again. If anyone knows how to, it would be great!!! THANKSSS!!!!!