Is there a way around using field level security to make fields not reportable, but still accessible on page layouts and formulas?

Is there a way around using field level security to make fields not reportable, but still accessible on page layouts and formulas?

I have written a C# application that forces territory rules to run on a scheduled time period by running the salesforce generated URL.  So I am trying to write a trigger that runs the territory rules when an Opportunity is either created or updated!  The problem is that I don't see a way to force the territory rules to run! 

Does any one have a practical solution?  BTW, I tried to update the account associated with the opportunity.  If I do it via Salesforce, the account page layout forces the territory rules to run.  This is due to the checkbox 'Run territory Assignment Rules on save by default' on the account page layout.  But, it seems this doesn't work via the API.

Any information on this matter would be greatly appreciated!