The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.
One of a set of tools we're offering as a way of saying thank you for being a part of the community.
There is, to the best of my knowledge, no easy way of doing what you want. To do this, you would need to throw away the Common Dialog control, call the Windows API directly, use a hook function, and use a few hundred lines of code.
That or lower your standards. Many commercial applications don't act like Word and Excel.