design report at runtime

I need to allow the user to design the report format at runtime. I'm
studying with what tools that I can do that.

The users need to design the report/document by themselves because they
are in different cities. They may have different names for the same
report/document. And the format may need to be changed over time.

Now I have the following options.
- Crystal Report
- Active Report
- Microsoft SQL Server Reporting Service
- Excel (optionally with Action Pane)
Maybe all of them can support that, just differ in the effort required.

We are going to use VS.NET 2005 although it's still in beta. We
haven't decided whether to use WinForm or WebForm yet. The only
consideration about this is that the WinForm may makes it easier to
realize the goal of designing the report format at runtime. As to the
deployment of WinForm application, we can make use of the Click-Once
deployment provided in VS.NET 2005 (or .NET Framework 2.0?).

Does anyone have any experience in designing report at runtime? Any
ideas will be appreciated.

Thanks in advance!
Zhu Ming