How can I use reflection map in windowblinds skin?

Hello,

I'm try to use the reflection map in a skin I'm creating. If I use a windowframe with borders having shadows the reflection map is covering all the borders even the shadows. If I use the content margin of the reflection map this values are applied to all borders, so if I use a top margin to fit the shadow length of the top border, the reflection map shows well for the top border but not for the others, because that value are applied too.

I appreciate any help over this issue. I'm using windowblinds 5.1

Thanks and sorry for my English,