title: decrement value in collection until 0
body: <p>I´m using <code>meteorJS</code> and have a <code>user collection</code> where I´ve stored a value called 'score' in the users profile.</p>
  
  <p>Now, I want to update the collection with a decrement of the score value by 10 for each user but I have problems with getting the score value for each user and update them like <code>"current value - 10"</code>. It also should only update the values that will not become lower than 0.</p>
  
  <p>Can someone give me a hint how to find and update the value for each user the profile?</p>