title: What is the algorithm to convert an Excel Column Letter into its Number?
body: <p>I need an algorithm to convert an Excel Column letter to its proper number.</p>
  
  <p>The language this will be written in is C#, but any would do or even pseudo code. </p>
  
  <p>Please note I am going to put this in C# and I don't want to use the office dll.</p>
  
  <p>For 'A' the expected result will be 1</p>
  
  <p>For 'AH' = 34</p>
  
  <p>For 'XFD' = 16384</p>