siebel running in different domain

Experts,

I have a desktop application and i try to open the siebel iframe from that application and allow the user to login to siebel. I am running into the issue where i am trying to run the desktop and siebel application run from different domains.

for example : I have desktop application Test and the siebel iframe, I am trying to run these two from different domain as (ie : siebel.mycompany.com and test.mycompany.com) or run these two from a common domain.

does this possible? I am able to make this solution working in same domain where my desktop application and siebel application run in same domain.