title: i want to use Powershell to subtract a numeric value (in a .csv file) in lets say ' B2' from an adjacent cell lets say 'C2'
body: <p>i want to use Powershell to subtract a numeric value (in a .csv file) in lets say ' E2' from an adjacent cell lets say 'D2' but only if the text in 'A2' starts with a letter C. the sum result should be displayed in 'F2', if 'A2' does not start with the letter C it copies cell 'D2' to 'F2'</p>
  <p>this should happen for all following rows</p>
  <pre><code>Serial         Date        Mono    Colour  Spotcol  result
  CNFL64383      07/07/2022  3994    19990   2167     17823
  74648160200FK  07/07/2022  771941  0       0        0
  VNF4J20449     07/07/2022                           0
  CNJL40076      07/07/2022  6369    3602    762      2840
  CNJK65021      07/07/2022  19431   10444   839      9605
  CNB3Q1NBJG     07/07/2022  199     171     0        171
  75280520H5VMT  07/07/2022  6532    12715   622      12715
  </code></pre>
  <p>Before:</p>
  <p><a href="https://i.stack.imgur.com/6vqY1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6vqY1.png" alt="enter image description here" /></a></p>
  <p>After:</p>
  <p><a href="https://i.stack.imgur.com/4Ua6g.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4Ua6g.png" alt="enter image description here" /></a></p>
  <p>any help would be greatly appreciated as this has been frying my brain for some time now :)</p>