I should have clarified the question further. It was misleading in that my 'work' network is not an intranet system. The machine in question is not a workstaton, just my personal laptop that I use for email.
Scenario: Files to be attached are rather large, located on a network with low external bandwidth (<5K/s). I want to use my 3G connection to send external emails, and for browsing, without disconnecting from the network drives.
To re-state:
I want to prioritize my LAN interfaces so that I can be connected to multiple networks while controlling which one is used for internet access.
Solution:
I manually changed the Interface metric for each connection available to my computer.
properties -> TPC/IP v4 -> advanced.
I used this method to set the order of preference, if available as follows
1 - "LAN 3" (3G device over USB)
2 - "bluetooth PAN" (3G device over BT)
3 - "LAN" wired ethernet (usually not conected)
4 - "Wireless" a/b/g/n (with network drives)
I only have one 3G device, but there are two ways that I can connect to it.
So, windows will stay connected to the wireless lan and have access to network drives, and slow internet, but will use my 3G device for internet, if available.
I hope this helps clarify the original question and possibly to help someone with a similar concern