I have searched up and down and could not find what I need. Several post on these forums have revealed themselves but nothing of use.

What I am trying to do is make a specific control have an adjust opacity value. I have tried using the technique for forms but it does not work with controls.
Code:
    Call SetWindowLong(theControl.hwnd, GWL_EXSTYLE, GetWindowLong(theControl.hwnd, GWL_EXSTYLE) Or WS_EX_LAYERED)
    Call SetLayeredWindowAttributes(theControl.hwnd, 0, bytOpacity, LWA_ALPHA)
I've been able to make the background completely transparent but I only need partial, or a way to fill behind the object with another transparent color.

The control I am trying to work with is an RichTextBox.