ActiveX and VBA
Developer's Guide > Create and Edit
AutoCAD Entities > Use Layers, Colors,
and Linetypes >
Assign Layers, Colors, and Linetypes to Objects
Once you've defined layers, colors, and linetypes, you can assign them to objects in your drawing. You can group associated components of a drawing by assigning objects to layers. You can control layer visibility, color, and linetype and specify whether objects on a layer can be edited. You can move objects from one layer to another and change the name of a layer.
The number of layers in a drawing and the number of objects per layer are virtually unlimited. You can assign a name to each layer and select any combination of layers for display.
You can define blocks from objects that were originally drawn on different layers with different colors and linetypes. You can preserve the layer, color, and linetype information of objects in a block. Then, each time you insert the block, you have each object drawn on its original layer with its original color and linetype.