How to Ensure that a Textbox Will Stay Alinged with a Matrix in SSRS 2008?

Question

Hello All,
I am very frustrated with this situation that I have at the moment regarding a matrix.  My matrix is laid out and styled the way that I like and it works, however I need to add a title above it and i've chosen to do this with a separate textbox. 
The problem I now have is that when I run the report, the textbox may or may not be the same length as the matrix. 
What method can I use to ensure that my matrix will always line-up correctly with my textbox?
In a very general way (screenshots are stupidly not allowed in this forum), here is what I am looking for:
                           WEEKLY SELL-OUT
Row Group  Column title 1    Column title 2   Column title 3
WEEKLY SELL-OUT is the title which I need.  I've put a rectangle around the matrix and tried aligning them, but each time the data is refreshed the matrix may or may not be aligned with the WEEKLY SELL-OUT textbox.
I've also tried putting a title within the left corner texbox within the matrix itself, however this is ugly and not what I want.  I need it to be centered with the entire matrix and not just withing the textbox. Doing it this way does this to my matrix:
WEEKLY SELL-OUT
Row Group  Column title 1    Column title 2   Column title 3
Again this is not what I want.  I want it to be centered and using the textboxes inside the matrix does not allow me to do that.  Also, i'm not able to merge cells within a row in a matrix, only within a column.
Surely there MUST be a way to do this properly - can someone help?

Answer 1

Seemed like a good idea -- to embed the matrix inside the lower cell of a 1-column, 2-row table -- but I couldn't get it to work.  When attempting preview, it resulted in an error -- "The tablix 'matrix1' has a detail member
with inner members.  Detail members can only contain static inner members."  The matrix works fine outside of the table.  I'm not sure if properties of the matrix or table could be adjusted to remedy the error.  The 'CanGrow'
property for the table is set to 'True'.
UPDATE:  It is critical to put the matrix in the
Header cell, not the
Details cell.  Delete the Details row (cell).  Create a new header row above the existing Header that contains the matrix in order to add a title and center it.