Positioning one source on top of another

[artmt]

I am trying to build a web site for my eBay store.
For browsing the inventory I want to use eBay's site, but still want
to display my store's navigation bar at the top.
If I create two frames (the smaller one on top containing my navigation
and the larger bottom frame pointing to ebay.com) I get my nav on top,
then eBay nav in the middle and only below the eBay content that I
actually want to display.
What I am hoping to achieve is that my nav goes over eBays. Doesn't
have to be aligned precisely.
In other words I want my own content to cover the top N lines of
whatever I am refencing.
Is there a way to achieve this effect?

Thanks
Art