title: Extend Formula Range Using Excel Interop
body: <p>I'm using the Excel Interop libraries to take a sheet and replace values in the sheet. My sheet structure is as follows:</p>
  
  <p>Columns A-E contain formula which work off the data in Columns F-L
  When I update the sheet, I clear the contents from F-L and leave any formula in A-E. I then fill columns F-L with new data.</p>
  
  <p>I need my formula in Columns A-E(any rows) to extend to the full range of the new data I entered.</p>
  
  <p>For example <code>=sum(G1,G8)</code> should become <code>=sum(G1,G20)</code> if I extend the data to 20 rows from 8.
  Is there a way to get to all present formula in the sheet? How do I extend the range of the formula?</p>