If the button is not an actual button (i.e., if it's drawn through code rather than using the standard Win32 button control) you're not going to be able to find it with Spy++. It won't be an actual window, so it won't have a window handle. Thus, you're also not going to be able to click it through the normal mechanisms, like sending it a BM_CLICK
message.
It's possible that they're doing this as a security feature, but it's also quite likely that this is part of the growing trend away from using the native UI controls, one that I very strongly disagree with and whose motivations I seriously question.
Your only hope is probably UI automation, which is very tricky to get right. Make sure to test the program in a virtual machine so the world doesn't end when you inevitably click the wrong thing accidentally.