gluPickMatrix

Hi,
I am working on the Picking mechanism that OpenGL supports.What I have is a three dimension wire mesh rendered.In order to modify this rendered wiremesh I am using gluPickMatrix().But,however hard I tried,the code siply doesnt seems to work.All those prerequisites have been taken care of.The steps that I followed is as under:

  1. Draw the wire mesh in the default mode first.
  2. On menu selection + on LButton down enter the selection mode,by defining the selection buffer then make projection matrix the current matrix and use gluPickMatrix()then use glFrustum().rerender the object in selection mode.and examine if a hit occured.

Can any one of u tell me how the viewing volume is defined once gluPickMatrix() is used??and the possible flaw in the code.

for the said problem is there any other way to achieve the goal???

thanx in advance.
Milind.