HBITMAP hBitmap1 = (HBITMAP) bitmap.GetHBITMAP();
COLORREF colorRef = PALETTERGB(maskColour.Red(), maskColour.Green(), maskColour.Blue());
return ImageList_AddMasked((HIMAGELIST) GetHIMAGELIST(), hBitmap1, colorRef);
HBITMAP hBitmap1 = (HBITMAP) bitmap.GetHBITMAP();
COLORREF colorRef = PALETTERGB(maskColour.Red(), maskColour.Green(), maskColour.Blue());
return ImageList_AddMasked((HIMAGELIST) GetHIMAGELIST(), hBitmap1, colorRef);