title: microsoft project 2010: failed to set field value when custom field has formula settings
body: <p>I have a question about setting a field value in Microsoft Project 2010. A custom field(text25) has formula settings, which is </p>
  
  <blockquote>
    <p>IIf([Baseline Estimated Start]=projdatevalue("NA"),"",Format([Baseline Estimated Start],"YYYY-MM-DD"))</p>
  </blockquote>
  
  <p>when I using Microsoft API to set this field's value, the code is as following, MSPField is the field with the formula setting.</p>
  
  <pre><code>MSProject.Task.SetField(MSPField, value);
  </code></pre>
  
  <p>This code will cause an exception:</p>
  
  <blockquote>
    <p>System.Runtime.InteropServices.COMException (0x800A044D): The argument value is not valid.at Microsoft.Office.Interop.MSProject.Task.SetField(PjField FieldID, String Value)</p>
  </blockquote>
  
  <p>How to fix this issue?</p>