title: Regular expression where part of string must be number between 0-100
body: <p>I need to validate serial numbers.  For this we use regular expressions in C#, and a certain product, part of the serial number is the "seconds since midnight".  There are 86400 seconds in a day, but how can I validate it as a 5-digit number in this string?:</p>
  
  <pre><code>654984051-86400-231324
  </code></pre>
  
  <p>I can't use this concept:</p>
  
  <pre><code>[0-8][0-6][0-4][0-0][0-0]
  </code></pre>
  
  <p>Because then <code>86399</code> wouldn't be valid.  How can I overcome this?  I want something like:</p>
  
  <pre><code>[00000-86400]
  </code></pre>
  
  <p><strong>UPDATE</strong><br>
  I want to make it clear that I'm aware of - and agree with - the <em>"don't use regular expressions when there's a simpler way"</em> school-of-thought.  <a href="https://stackoverflow.com/questions/1909528/regular-expression-where-part-of-string-must-be-number-between-0-100#1909559">Jason's answer</a> is exactly how I'd like to do it, however this serial number validation is for all serial numbers that pass through our system - there's currently no custom validation code for these specific ones.  <em>In this case</em> I have a good reason for looking for a regex solution.</p>
  
  <p>Of course, if there isn't one, then that makes the case for custom validation for these particular products undeniable, but I wanted to explore this avenue fully before going with a solution that requires code changes.</p>