Column header of matrix keeps repeating

Hi there,

I'm using SSRS through Visual Studio 2005 however I am very much a novice at this and need to work out how to solve a problem.

I have a matrix which looks like this:


Area                                              Column header
                   Row header 1
                   Row header 2
                   Row header 3
                   Row header 4


In my column header is a field where the date of each week beginning is populated in a number of columns as headers left to right.
This whole matrix repeats with each area field, however I would only like the column header with week beginning dates appearing on the first area matrix at the top of the page, and not every single one (otherwise the week beginning dates are being repeated 4-5 times per page where once at the top is enough.)

I am trying something like =IIf(RowNumber("ColumnGroup") =1. Fields!WeekBegin.Value, "") in the expression but it doesn't seem to work, I think it doesn't like "ColumnGroup". Not sure if this expression is even right.

Any suggestions / solutions? (Apologies if I haven't explained it very clearly, as I said I'm pretty new to all this!)