Here are several sermons that you may find helpful if you are wondering whether we believe God ever communicates to us with words that are not in the Bible:

• Using Our Gifts in Proportion to Our Faith, Part 1: The Gift of Prophecy
• When Will Prophecy Cease?
• The Authority and Nature of the Gift of Prophecy
• Why the Gift of Prophecy Is Not the Usual Way of Knowing God's Will

 

The following article takes the position that God does not speak to us other than in the Holy Scriptures and that the canon is now closed and finished.

http://www.the-highway.com/God_Speak.html

 

The following articles discusses views on exactly how God communicates outside of the Bible:

http://voiceofthesheep.wordpress.com/2007/01/22/outside-of-the-bible-exactly-how-does-god-speak/