How to - Open a photoshop document - Interface or suit - for plugin

Hello friends,
Kindly help me...
If we know the path to the document, is there any suit or interface available in photoshop cs2's sdk for opening a document in photoshop window?

We are developing phtoshop automation plug-ins, to all user to encode and decode photoshop documents automatically. for that we are adding 'Decode and Open' and 'Encode and Save As' menu under FILE->Automate menu, and all user to Select document to open and saveAs.
We are able decode the selected document, we are saving that to users temporary folder, but could not open the decoded document in photoshop's (layout) window.
Is there any suit or interface available in photoshop cs2's sdk for opening a document in photoshop window?

Thanks in advance
Sachin