VBA how to check for layers and create some?

Simple question.

What I want is when the user clicks a button, a macro will execute some vba code and check if the current drawing has/has not some layers in it...like layerA, layerB, layerC. If the drawing does not have those layers, then create them for the current drawing.

Any help?Advice? Thank you.

Ok...So I've managed to do that...But the question now is how to set the color of the linetype of the layer? It's something like

ThisDrawing.Layers.Item(counter).TrueColor=??????

I believe AutoCAD 2004 has the older .color property still avaialble, though not listed in the help files.

The newer .TrueColor can be modified by first creating the object:

Set color = AcadApplication.GetInterfaceObject("AutoCAD.AcCmColor.16")

then modifying the properties accordingly:

Call color.SetRGB(80, 100, 244)

finally:

ThisDrawing.Layers.Item(counter).TrueColor = color

Code taken from the Developer Documentation Examples