title: Opencart - file option and price calculation
body: <p>i'm trying to make e-shop for business cards, brochures and etc printing. So main option is file upload option.
  The problem is that opencart not recalculating prices if user uploaded different files. Lets say customer want to order 100 business cards with one picture (price is 0.2$ each when amount is 100 ) and 1000 business cards with another picture (0.1$ each when amount is 1000), in total it should be 120$, but opencart showing 110$ :</p>
  
  <p>-business card (file1.pdf) x100  0.1$</p>
  
  <p>-business card (file2.pdf) x1000  0.1$</p>
  
  <p>Total 110$</p>
  
  <p>i want that prices would be recalculated if uploaded files are not same :</p>
  
  <p>-business card (file1.pdf) x100  0.2$</p>
  
  <p>-business card (file2.pdf) x1000  0.1$</p>
  
  <p>Total 120$</p>
  
  <p>How can i do this?</p>