AutoCAD .NET :: Custom Dimension Of Coordinate String

I want to custom dimensions about text of the coordinate in DWG. It should be like this:

I select a point then there displays a string of X,Y,Z coordinate of the point.

I select the second point to place a horizontal line(fixed lenth base the string font size)  and then the string.

the whole process is like radialDimension,but what I need is to describe the point x,y,z.

and the drawing should consist of start point(actually is the target point too) and end point and the line connects the two points and a horizontal line and a string.

I think this should be completed using Dimension Class(should be CoordinateDimension based Dimension).

give me some codes. Codes is better in C# of VS2010 for autoCAD2010.

Actually there is a simple solution for this. Using c# to draw two lines and a string. But this is really bad experience when I want to move the string.