If you are not interested in the background of my question please skip to 'QUESTION:'.

I have developed many systems using (Visual) FoxPro. For the first time I have to develope an information system with VFP 5.0 as front-end and SQL Server as the back-end application.
Because my knowledge of developing client/server applications with SQL Server is relatively low it is hard to make the write important decissions of how to start things.
So i read a lot of stuff and found out that i can communicate with SQL Server with remote views (ODBC) or SQL pass-through.

My client finds it very important that business-rules are centrally defined because in the future multi-clients will communicate with SQL Server for the same database. Therefor, if business-rules change, code should only be changed on one place.

I thought i found the solution! I can use SQL pass-through to call SQL Server stored procedures. When business-rules change only code in the stored procedure of SQL Server had to be changed.

But many people are talking about multie-tier architecture these days. So in order to make the right decissions i had to find out more about it. I read documentation from Robert Green about thrie-tier architecture. It says i can write my business rules in Visual FoxPro and make it an OLE object. This OLE object can be installed on a seperate OLE server. Since most programmertools can communicate with OLE objects, writing the business rules in the OLE object would also satisfy my client.
Now i have to decide wether to call SQL Server stored procedures or to use three-tier architecture with an OLE Server.

QUESTION:
What could be a reason to use three-tier architecture with an OLE Server rather then calling SQL Server stored procedures?

I know one is that i can write business-rules in my familair language VFP but i wouldn't realy care to learn SQL Server language.

I have been thinking about a possible pro of using multi-tier architecture but i am not sure this is true: Can i develope OLE objects like navigation buttons where for instance the skip button is disabled when the end of the file is reached and use this object in Visual FoxPro Access and Visual Basic?

I realy need to know the pros and cons in order to make the right decission.

Thanks for any reply,

Marco.