title: set drop-down values based on vlookup
body: <p>I have a worksheet <code>UserEntry</code> with 2 columns, <code>Block</code> and <code>Address</code>.  I want to validate both of these based on another worksheet <code>Validation</code> with the same column names.  The data on the <code>Validation</code> sheet is as follows:</p>
  
  <pre><code>Block | Address
  ---------------
  001   | 101
  001   | 101.3
  001A  | 35
  020-1 | 203
  020-1 | 203.5
  020-1 | 204.1
  
  ...
  </code></pre>
  
  <p>There are about 11000 different blocks, and about 40000 block/address pairs.</p>
  
  <p>My goal is that if a user enters a value into the <code>Block</code> column on the <code>UserEntry</code> sheet, the drop-down choices in the <code>Address</code> column change to correspond with that <code>Block</code>.</p>
  
  <p>I tried using Custom validation with this formula:</p>
  
  <p><code>=VLOOKUP(UserEntry!A2,Validation!A2:B40000)</code></p>
  
  <p>But that evaluated to an error.  I saw some solutions in various forums that involved setting named ranges and then having the VLOOKUP() search for the appropriate named range, but it seems like that won't work here because I'd have to create 11000 named ranges.</p>
  
  <p>How can I make the validation drop-down for <code>Address</code> include all the values corresponding to a given <code>Block</code> value? </p>