title: VBA Not IsNull
body: <p>Working with some VBA code in Access that when a very specific set of conditions are met it will pop up an InputBox asking for a integer. So far so good.</p>
  
  <pre><code>Private Sub Command10_Click()
  
      If Not IsNull(mrf) Then
          If min &lt;&gt; max Then
              If qty &lt;= min Then
                  mrf = GetParamValue
              End If
          End If
      End If
      End Sub
  </code></pre>
  
  <p>The problem is that the Not IsNull seems to be ignored. I would like it to ask for a value to be entered unless a value is already present. This keeps firing off the InputBox as long as the min &lt;> max and qty &lt;= min conditions are met. What am I missing here?</p>