How to acomplish the following scenario?

[eluser]CKLFP[/eluser]
Hi, every one.

In trying to do the following:

Imagin you are at http://www.domain.com and you are admin of that site and you click on the admin button,
a modal window comes you enter the login data, for the sack of this exemple every thing goes ok.
Now you are redirect('http://admin.domain.com).
My question is how can I pass the user to the new URL because he is tested in http://www.domain.com

I'v try to use flashdata but when I reach the controller in new URL I can't read it but she exists in the session database, I can see it.

This is the stucture

out of web root
CI
application
...
modules
apps
backoffice(http://admin.domain.com)
frontoffice(http://www.domain.com)
...
system

I'm reaching one or another using $routes['']. with an if(sobdomain) condition.

Thanks I realy hope some one can help because the is the secound day trying to do this and nothing, I'v google it I'v stackoverflow it, I'v test untest write delete so much code my fingers are in blood well almost.

[eluser]CKLFP[/eluser]
Never mind I finally maged to do it

Thanks for nothinng