Adobe Illustrator screen transparent convert to WPF

Question

I designed my user interface in Adobe Illustrator. I am using Microsoft expression design 4 to convert it to Xaml. Everything looks good, but the Xaml does not look right with the objects whose transparency is set to Screen. It looks excellent in Microsoft expression design 4, but not in Microsoft Blend. Has anyone had this problem before? Does anyone know how to replicate Adobe Illustrator's screen transparency into Xaml?