A custom DecimalBox for accepting only Digits and a Decimal Point

I'm actually a full-time investor who writes financial and stock analysis software. In past careers I was a digital design engineer, network-management engineer, Active Directory design engineer for million-user networks, DNS & DHCP specialist, chief trouble-shooter for computer network hardware and software anomalies and problems for million+ user networks, and in a previous life, a US Naval Security Group telecommunications specialist. I am first and foremost, someone who loves solving problems, the larger, the better, the more systemic and complex, the better. I've programmed on and off since 1977, and am embracing C#.