Using the win32 ole (I'm using the perl implementation if it matters, though I could be persuaded to use a different language for this part of my project) can I interact with a window I didn't create?

I'm writing a Win32 program with MSVC++ 6.0. The whole user interface is just one Dialog Box which I created with the resource editor. My question is, how can I set/add an icon to the title bar of the ...