Setting Focus in Dialog

Hello, I have a custom control that can only be set as the first window to receive messages (from keyboard, mouse, etc...) using the "tabstop" feature. So if I set the custom control to be tabstopable then I can switch which custom control window receives the messages.

I think this is unintuitive for a user of the application, and I'd like it to be so that if a user clicks on my custom control it will active it as the "main window for receiving messages" so that when the mousewheel is moved and keyboard presses happen it gets the messages.

This is a dialog application. (control sits inside a dialog window)


My question is just... how do i do what tabstop is doing to set the window?

I've tried SetActiveWindow() SetFocus() SetForegroundWindow()... nothing seems to work :(

EDIT: I should mention I am working with the Win32 API.