You know Rich, when you stated ..... "Same as the other three posts on the controller your on your owne."
I am assuming you're trying to tell me that I am on my own and no one will help me?
Pretty crappy attitude if you ask me, and after spending almost four years messing around with this I think it is evident that I am on my own and that no one is willing to help.
As a hobby, this sucks.
Unless you know people or are in the trade don't take up the hobby, no one will help you and most people involved are anti-social. (That's just my experience over the last few years)

I've answered this several times, in several places.
You need to write a Mach3 plugin for the device you want to use.

Fwiw, there are several USB devices which work with Mach3. It's up to the hardware developer to write a plugin for Mach3 to use their hardware.

Where have you answered this can you provide me with some references so I can view the answers?
I want to use Arduino, what do I flash the AVR with? What is the sketch supposed to look like? How do you write a plugin for a micro, specifically the Arduino?
Phidgets would be a VB.NET, C, C++, C#, Python, Java, Pearl, (to name a few) program that works with the library provided, no flashing a micro so yeah I can see a plugin being written in one of the languages I noted, but Arduino dosen't have any libraries, so again how do I deal with the packets? How do I intercept the packets?

You say there are several USB devices that work with Mach, what are they? It's one thing to claim things work, it's another to reference them.
Anyone can say they are a doctor, not everyone can prove it.

I want to use Arduino, what do I flash the AVR with?

Basically, your on your own, and you'll need to write your own code, as I'm not aware of anyone using an Arduino for motion control with Mach3. It really makes no sense, as a parallel port offers better performance than you'll get from an Arduino, and all you have to do is plug it in.

How do you write a plugin for a micro, specifically the Arduino?

You study the available samples, and figure it out. Writing a plugin is not a trivial task. I have no idea how to write one.
You asked how to use your Phidgets with Mach3. A plugin is the answer. You didn't ask if someone would do all the work for you.
As far as I know, you don't "intercept" any packets. Your plugin should send the required data to the device.

You say there are several USB devices that work with Mach, what are they? It's one thing to claim things work, it's another to reference them.

Smoothstepper - www.warp9TD.com
KFLOP - www.dynomotion.com
Nevex - http://www.nevex.com.br/
PureLogic - http://www.plmotion.com/

There are others as well as ethernet motion controllers that work with Mach3. All interface with Mach3 via a plugin.

Pretty crappy attitude if you ask me, and after spending almost four years messing around with this I think it is evident that I am on my own and that no one is willing to help.
As a hobby, this sucks.
Unless you know people or are in the trade don't take up the hobby, no one will help you

Tens of thousands of people are using Mach3 with the parallel port, or with one of the USB or ethernet motion controllers I mentioned above. You want to do something that NOBODY ELSE is doing. Because of that, yes, you are on your own.
By a $20PC with a parallel port on Ebay, or one of the motion controllers that already work with Mach3, and you'll get all the help you need.

Ask questions about topics that are obviously way over your head, and then argue with people that try to steer you in the right direction, and no, you won't get any help.