draw a line on a plane

[Dastagir]

hi friends,

i would like to draw a line on a surface ,where it should show the depth..i'm having on the two vertex for line..

eg : glVertex3f(0.0f,0.0f,0.0f);
glVertex3f(2.0f,0.0f,0.0f);

http://cid-6a2ae6c2240ebc3b.skydrive.live.com/self.aspx/New%20album/line.bmp

In this image the line is drawn with depth..

According to the dynamically generated vertex i want to draw on the surface..help me regarding this