title: Open a Workbook that is in the background
body: <p>I'm trying to open a workbook that is in the background. </p>
  
  <pre><code>Dim app As New Excel.Application
  app.Visible = False
  Dim book As Excel.Workbook
  Set book = app.Workbooks.Add(UserForm1.TextBox1.Text)
  </code></pre>
  
  <p>I get the filename out of a textbox. </p>
  
  <p>I get a crash at:</p>
  
  <pre><code>Sheets("Start").select
  </code></pre>
  
  <p>I guess the workbook in the background is not the active one. How can I activate it?</p>
  
  <p>My idea was: </p>
  
  <pre><code>Workbooks(UserForm1.TextBox1.Text).Activate
  </code></pre>
  
  <p>But I only have the filename, not the whole path and filename.</p>