You're in luck. There are two ways to adjust the volume levels of commercials. The first is VOL -. The second is Mute.
Sorry, but there is currently no way to automatically decrease the volume levels of commercials. Some TV's have AVL (Auto Volume Leveling), but I haven't found this feature to be very helpful. The loudest commercials I am aware of are the ads running in the background while navigating the On Demand menus. Is this what you are referring to, or is it a particular channel?
Here's my workaround.
Bose SOLO TV Sound System works with my QIP 7100 1
SOLO is hooked up to the Optical Audio Output of the QIP
1) Adjust TV Volume to a "low" volume that you want.
2) Use volume control on SOLO adjusted to your TV listening and viewing level.
3) When you want to "partially" mute your TV just mute the SOLO
4) Very useful also when the phone rings.
If you turn off the TV before you turn off the SOLO , the program audio will still be "piped" to the SOLO via the QIP Optical Audio Output
This was a " fringe benefit " when I decided to get a Theater Sound from my TV system.
The Bose SOLO has added greatly to the enjoyment of "watching" TV programs.