User defined number ranges
<p>I have a function where for a specific number range a percentage has to be applied:</p>

<ul>
<li>0-100 EUR: 5%</li>
<li>>100 EUR: 3%</li>
</ul>

<p>This number ranges and percentages should be <strong>user-defined</strong>.</p>

<p>The implementation should be as simple as possible.</p>

<p>What would you suggest for specifying the ranges and calculating the result?</p>
