Is it possible to launch IE's proxy settings dialog from the command line?

I've found another one, shorter:

inetcpl.cpl ,4

You can use it in Run box or Command Prompt.

Okay, I made a 15 minutes research for you and got following commands and a link.

To Open Internet Settings

inetcpl.cpl

To Open Internet Settings with Connections Tab

rundll32.exe shell32.dll,Control_RunDLL inetcpl.cpl,,4

For more information http://discussions.virtualdr.com/archive/index.php/t-41613.html

The closest I can get is

control inetcpl.cpl,,4

which opens the Internet Properties dialog with the Connections tab preselected. Unfortunately it still requires you to click on LAN settings to get to the proxy settings.