There is a Link web part and a Page viewer web part on the web part page. The requirement is that, whenever a user clicks on a particular link inside Link Web Part it should automatically render the corresponding page inside the page viewer web part.
By default the page viewer web part does not support connections.
The solution is to create a page viewer web part that accepts the url as the connectable parameter. There is an interesting post by Todd Baginski about creating a connectable Page Viewer Web Part
Even though the code-sample mentioned in the above link is for SPS 2003, we need to do code changes if we are developing it for WSS 3.0 / MOSS 2007. Probably if we are developing the web part as “SharePoint web part” the code changes we’d be making is less, compared to developing it as “ASP.NET” web parts.
I’d try this developing it for WSS 3.0/ MOSS 2007 and share my experiences