im not familiar with automation ... couldnt you create a dxf file ? and import it ? to .cad ?

http://en.wikipedia.org/wiki/AutoCAD_DXF

^^^ wiki file definition info

Application ID (APPID) table
Block Record (BLOCK_RECORD) table
Dimension Style (DIMSTYPE) table
Layer (LAYER) table
Linetype (LTYPE) table <<<<<<<<<< ???
Text style (STYLE) table
User Coordinate System (UCS) table
View (VIEW) table
Viewport configuration (VPORT) table