title: Excel formula-based lookup for multiple criteria across multiple sheets?
body: <p>I have a series of tabs formatted uniformly that contain data that I want to consolidate onto one master data sheet. I'd like to do this without indexing/looking up each sheet individually.</p>
  
  <p>I've created a sample to illustrate the challenge I'm having in searching for data across multiple tabs to create a master data dump. Given the 4 worksheets shown below, the <em>Summary</em> tab has pre-filled values and I'm trying to fill in for the values marked with <code>???</code> if possible.</p>
  
  <p><strong>John:</strong></p>
  
  <pre><code>         | Month 1 | Month 2 | Month 3
  ---------------------------------------
  Sales    | 500     | 1000    | 800
  Expenses | 200     | 300     | 250
  Total    | 300     | 700     | 550
  </code></pre>
  
  <p><strong>Joe:</strong></p>
  
  <pre><code>         | Month 1 | Month 2 | Month 3
  ---------------------------------------
  Sales    | 400     | 800     | 600
  Expenses | 300     | 280     | 225
  Total    | 100     | 520     | 375
  </code></pre>
  
  <p><strong>Mary:</strong></p>
  
  <pre><code>         | Month 1 | Month 2 | Month 3
  ---------------------------------------
  Sales    | 750     | 850     | 900
  Expenses | 275     | 325     | 400
  Total    | 475     | 525     | 500
  </code></pre>
  
  <p><strong>Summary:</strong></p>
  
  <pre><code>Agent | Period  | Sales | Expanses | Total
  -------------------------------------------
  Joe   | Month 1 |  ???  |    ???   |  ???
  Joe   | Month 2 |  ???  |    ???   |  ???
  Joe   | Month 3 |  ???  |    ???   |  ???
  John  | Month 1 |  ???  |    ???   |  ???
  John  | Month 2 |  ???  |    ???   |  ???
  John  | Month 3 |  ???  |    ???   |  ??? 
  Mary  | Month 1 |  ???  |    ???   |  ???
  Mary  | Month 2 |  ???  |    ???   |  ???
  Mary  | Month 3 |  ???  |    ???   |  ??? 
  </code></pre>