XAML Combine Styles

Is there any way to combine mutliple styles in XAML to make a new style that has all of the desired settings?

For example (pseudo code);

<Style x:key="A">
 ...
</Style>

<Style x:key="B">
 ...
</Style>

<Style x:key="Combined">
 <IncludeStyle Name="A"/>
 <IncludeStyle Name="B"/>
 ... other properties.
</Style>

I know that there is a 'BasedOn' property for styles, but that feature will only take you so far. I am really just looking for an easy way (in XAML) to create these 'combined' styles. But like I said before, I doubt it exists, unless anyone has heard of such a thing??