title: web2py - generate multiselect list
body: <p>I have an application using web2py.</p>
  
  <p>I have a table in the database called member:</p>
  
  <pre><code>db.define_table("member",
    SQLField("membership_id", "integer",notnull=True),
    SQLField("first_name", "string", notnull=True,length=100),
    SQLField("region", db.region))
  </code></pre>
  
  <p>and I want to display the region field as multiSelect list.</p>
  
  <p>How can I do this?</p>
  
  <p>Thanks in advance.</p>