How can i change the position of the near clipping plane?

Questions & Answers
1

How can i change the position of the near clipping plane without changing the position of the far clipping plane?

2

Far plane is always grater than near plane. If you try to set the near plane to a value grater than far plane then far plane will change automatically. So as far as I can think the answer to your question is just select a value less than far plane.

public void SetNearClippingPlane(Camera cam, float value)
{
    if(value < cam.farClipPlane)
    {
        cam.nearClipPlane = value;
    }
}