Image Overlay problems

[treckstar]

Hey everyone,

Right now I have an image that is being displayed as a header for my site. It is being displayed using css.

#header-group {
  background: url(../images/header.png) no-repeat top center;
  width: 978px;
  height: 115px;
}

What I would like to do is place another image "png" overtop of this background - having this image pushed to the right 312px and from the top 45 px.

I have been playing around with this forever and cannot find the best way to use this image. Does anyone have insight for me?

Thank you.