title: how do I reference a text box value in an expression? SSRS
body: <p>I have a list and inside this list I have a text box.</p>
  
  <p>Since it's a list, the text box value changes for each row in the dataset. </p>
  
  <p>OUTSIDE this list, I have another text box which is part of the HEADER.</p>
  
  <p>I want the HEADER to change based on the value of the text box in the list.</p>
  
  <p>In the text box in the header, how do I reference the text box inside the list?</p>