Depending on what you want to do and if you want to use AutoCAD or not, you've got some options:
1. With AutoCAD: Make an ObjectARX program in C++ to make .dwgs
http://usa.autodesk.com/adsk/servlet/index?id=773204&siteID=123112
2. Without AutoCAD: Make a program in whatever language to make .dxfs
Regards, Jake
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http://thatcadguy.blogspot.com/