Launch Xwindows / Gnome into single application

Hello All,

I'm trying to create a setup whereby when a user logs in x-windows automatically launches an application (in the case the CITRIX ICA Client) and when that application is closed, this ends the xsession and logs the user off.

This can be acheived when the user logs in via the text-based log in using a shell script which issues
startx /usr/lib/ICAClient/wfica (the path to the ICA client)
waits for the xsession to finish then logs the user out.

However, in order to satisfy branding requirements and the ability for the users to easily shut the system down I want to use the graphical logon. This prevents the previous method from working however, as the X Server is already running.

Has anyone tried something like this before? The important factors are:
1. Users cannot open any other programs
2. They are logged out when ICA Client exits
3. We can use the graphical logon (or something similar)
4. User can shut the PC down without be logged on (or a similar mechanism)

I am currently using Mandrake 10.0 and Gnome.
The ICA client will run in full screen, so there is actually no need for any particular window manager (or any at all!).

Oh my, that sounds complex!!

Thankyou for you time!

so i assume that you all are running in run level 5?
if so, then edit your /etc/rc5.d files to run that startx command