Just export .indd to RTF [Rich Text Format] and open this .rtf file through Word, then save it as .doc file.
Or you need something different....
Need sample scripts to Export .rtf from .indd files
Your standard InDesign installation comes with sample scripts.
For any further information, go to http://www.adobe.com/products/indesign/scripting/ -- open the Scripting Resources tab, download the PDFs for your version, read these cover to cover:
Adobe Introduction to Scripting
Check out this informative primer on why, how, and when to use scripting in Adobe Creative Suite® 5 applications.
Adobe InDesign CS5 scripting tutorial
Learn the basics of InDesign CS5 scripting in this detailed tutorial.
InDesign CS5 in-depth scripting guides