I am using all X10 modules. I want to prevent Dimming if someone tries to do it in Active Home Pro or on their IPhone using Active Phone.
There is no real way to lock out dimming unfortunately. The closest that you can get is using ActiveHome Pro and changing the Lamp Module/Wall Switch to an Appliance Module (2-pin). That way, AHP believes it can only turn the light on/off, and that it does not support dimming (like an Appliance Module). Be forewarned that if you have any Macros or other functions that depend on AHP knowing that it's really a light and not an appliance, those will no longer work. AHP will believe it's just an appliance, and only an appliance.
Otherwise, dimming won't be a function in ActiveHome Pro, and thus, dimming wouldn't work form ActivePhone.