I am looking for a way to pull data OUT of Excel XP (Excel 2002) in real-time.

Data are scattered in different worksheets belonging to one workbook and
come from a real time feed on which is applied some calculations (excel
formulas).
I'd say there are about two hundred cells to monitor.

What I need to do is to pull out those data as they change (in real-time).
The excel GUI must remain responsive as users may need to input data
themselves.

At first I was considering using the 2.0 .NET framework and Excel PIA to
subscribe to the Worksheet_Change event (or any other...), but I fear (from
my first test) the Excel UI might become non-responsive.

I was also considering looking into VSTO (Visual Studio Tools for Office)
but I'm not familiar at all with it so I'm looking for advice. From what I
understood, VSTO won't work with Office XP but upgrading to higher version of
Office is an option.

Basically I am an experienced .NET developer with no experience in Office
development, so any piece of advice is welcome.