title: Why can't an user-defined function take integer arguments and return integer?
body: <p>The following user-defined function cannot be used in the worksheet. When I type </p>
  
  <pre><code>=Add2(1,1)
  </code></pre>
  
  <p>it returns #REF.</p>
  
  <pre><code>Function add2(x As Integer, y As Integer) As Integer
      add2 = x + y
  End Function
  </code></pre>
  
  <p>If I change Integer to Double, only then it works. Why can't integer be used? Thank you.</p>