title: Cross-sheet search and conditional replace
body: <p>I am a casual Excel user, familiar with basic cell formulas and a few of the built-in functions, but have no idea how to approach this problem.
  I've been given a workbook with two sheets. The first sheet has over 10K rows of data across a bunch of columns. Columns D, G, and H are of interest.  </p>
  
  <p>Columns G and H each have 3-character symbols, treated as a pair, so for example, G12, and H12, G56 and H56. The symbols are not unique, but the pairs are. Column D contains the same word, TEST. So we have something like this:  </p>
  
  <pre><code>--D--   --G--   --H--  
  TEST    ABC     LMN  
  TEST    ABC     XYZ  
  TEST    GHI     LMN  
  TEST    JKL     QRS  
  TEST    LMN     JKM  
  TEST    LMN     XYZ  
  TEST    UVW     AMB  
  </code></pre>
  
  <p>The second sheet has about 2800 rows of two columns A and B, containing the same type of 3-character symbol pairs. They are not ordered, but we do know that every pair on Sheet 2 is somewhere in Sheet 1, e.g.</p>
  
  <pre><code>--A--   --B--  
  GHI     LMN  
  UVW     AMB  
  ABC     XYZ  
  LMN     XYZ  
  </code></pre>
  
  <p>For each symbol pair on Sheet 1, I need to determine if that pair is on Sheet 2 and, if so, the corresponding TEST in column D needs to be changed to DONE. So the result would be:  </p>
  
  <pre><code>--D--   --G--   --H--    
  TEST    ABC     LMN  
  DONE    ABC     XYZ  
  DONE    GHI     LMN  
  TEST    JKL     QRS  
  TEST    LMN     JKM  
  DONE    LMN     XYZ  
  DONE    UVW     AMB  
  </code></pre>
  
  <p>Does anyone know of a fairly straightforward way to do this, maybe with built-in Excel functions? This is a one-time thing, so I don't need anything too fancy or "future-proof.
  Dan</p>