subclassing static control to receive WM_CTLCOLORSTATIC - c++

Question

I want to make the background of a static control that displays text transparent. After 2 days of excessive googling i've come up with this:
class TLABEL : public TWINDOW {
private:
HINSTANCE hInst;
public:
static LRESULT CALLBACK SubclassCallback(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR userdata)
{
TLABEL* pThisWindow = (TLABEL*)userdata;
//look for messages that we want to process ourselves
switch (msg)
{
//make background transparent
case WM_CTLCOLORSTATIC:
{
HDC hDC = (HDC)wParam;
SetBkMode(hDC, TRANSPARENT);
SetTextColor(hDC, RGB(0, 0, 0)); //text color black
MessageBox(NULL, L"WM_CTLCOLORSTATIC", L"Error!",MB_ICONEXCLAMATION|MB_OK);
return (LRESULT)GetStockObject(NULL_BRUSH);
}
case WM_ERASEBKGND:
{
return TRUE;;
}
//remove Subclass if window is destroyed
case WM_NCDESTROY:
{
RemoveWindowSubclass(pThisWindow->handle, &TLABEL::SubclassCallback, uIdSubclass);
return TRUE;
}
}
//deliver all other messages to the original callback-function
return DefSubclassProc(hWnd, msg, wParam, lParam);
}
//standard alignment left
explicit TLABEL(int nx, int ny, int nwidth, int nheight, HWND hParent)
{
hInst = GetModuleHandle(NULL); //i know this is a bad practice
handle = CreateWindowEx(WS_EX_TRANSPARENT, //background transparent
L"STATIC", L"", //class name + text
WS_CHILD | WS_VISIBLE | SS_LEFT, //styles
nx, ny, nwidth, nheight, //dimensions
hParent, NULL, hInst, NULL);
//subclass window to catch messages we want to process ourselves
SetWindowSubclass(this->handle, &TLABEL::SubclassCallback, 0, (DWORD_PTR)this);
}
Somehow the SubclassCallback()-function never receives a WM_CTLCOLORSTATIC message, but i know that the function is called and that it receives WM_ERASEBKGND messages just fine. If i handle the WM_CTLCOLORSTATIC message in the message-handler of the main-window it works, unfortunately that would negate all benefits that come with making a seperate class for such a static control
I have not found any hints why the WM_CTLCOLORSTATIC message is sent to the main window and not my static control since all examples seem to do it just like that.
i have compiled it under VS2010 Express on a WinXP-32 machine