Display Change Password Dialog Box

We have a client that has a very large number of users that will be connecting back to the domain via VPN only. The problem is that the communications vendor can not pass the password expiration notice back to the client. What we would like to do is run a script or application after the vpn tunnel is established that checks the number of days remaining before the password expires and then give the user a prompt to change their password when a specified numbers of days is reached. Once the user acknowledges the prompt the script/application would display the change password dialog box that is displayed after pressing CTRL+ALT+DEL and select change password. We are able to calculate the number of days remaining for the password and start the script but have not found a way to launch the change password dialog box. An option is to write our own dialog but the client would prefer to have as little custom written code as possible. Can anyone please tell me if it possible to display the Change Password Dialog Box

Thanks
Greg