title: How to update database using the form value & calculation in Django?
body: <p><em>Currently using sqlite that comes with Django.</em></p>
  
  <p>In a <code>CreateView</code> of creating a <code>project</code> I want to search for <code>tools</code> that are in the <code>tools</code> database. Upon selecting one, it will display information in a row within the <code>CreateView</code>. Upon submitting my <code>project</code> I want to <code>-1</code> from the <code>quantity</code> of that <code>tool</code> in the <code>tools</code> database. </p>
  
  <p>In reference to my title I am just looking to subtract the value of in the  quantity input from the <code>tools</code> database and how to do that.</p>