How to publish excel document on Excel Services with 30 sheets on Sharepoint 2010 effectivelly (various sheets for different users)

Question

Hi,

I need to publish excel file on Excel Services. The file has data connection to a 500MB sql server table trought connection string. The document contains reports which are designed just for view by various users/groups. There are following requirements:

-the excel file has 30 sheets. Different sheets have to be published for different sharepoint groups with different permissions (view or no access mostly)
-process of publishing should be relatively easy
-users can't refresh data connection
-data refreshs are made by document owner on schedule (once a week) or manualy
-users can't download file, snapshot or edit file (sheets)
-users can't print file  (this probably will be achieved by AD RMS)


I've prepared document library with folders with appropriate permissions (groups with view only). Sheets or named items are then published to these folders. This works fine but the problem of this solution is that publishing takes considerable amount of document owner's time.

Is there any way to do this by publishing document just once and give user access to document's sheets or named items for example trought web parts?

Are there any other possible ways to do this?

What is the best way?

How to automate the process of publishing?