title: Find string and get its column
body: <p>Let's say I have a lot of columns and one of them contains "impressions" string (on row 3). What I need to do is to:
  1) Find the cell with "impressions" string
  2) Get column number or i.e. "D"
  3) Based on what I got paste a formula into i.e. D2 cell which gets AVERAGE from a range D4:D*last*</p>
  
  <p>I couldn't find it anywhere so I have to ask here without any "sample" code, since I have no idea on how to achieve what I want. (3rd one is easy but I need to get that "D" first)</p>