How should I do though it wants to output the sound that puts out only the main output from the audio interface and monitors it from the headphone terminal of PowerBook though I want to make the dj patch?
It sounds like you're trying to use both the powerbook headphone output
and an external interface at the same time with MaxMSP. To do this, you
need to set up an "Aggregate Device" (this works for OS 10.4+ only).
Open the "Audio MIDI Setup" application, and select "Open Aggregate
Device Editor" from the file menu.