title: Getting Overall row total in column total
body: <p>I have a Matrix and I need to get the total rows so I can perform a percentage.</p>
  
  <p>This is a rough matrix layout</p>
  
  <p>[MyDataSet]</p>
  
  <p>[MyParentGroupRow]</p>
  
  <p>[ColumnA] [ColumnB] [ColumnC] - [Row Total]</p>
  
  <p>[Column Total A] [Column Total B] [Column Total c] - [Overall Total Rows]</p>
  
  <p>So I need to take [Column Total x] / [Overall Total Rows]</p>
  
  <p>I can't seem to get the [Overall Total Rows value]. If I use the root dataset it will be wrong because the Tablix is filtered. So I need to get the total rows for [MyParentGroupRow].</p>
  
  <p>Notes.
  I can't change the dataset.
  Everything is a count of rows. So I can't use things like sum.</p>