Vista - StaticResource markup extension with Binding

Hi~~

I try to use StaticResource with Binding
Ex 1.
<Grid.Resources>
<SolidColorBrush Color="Red" x:Key="Hola"/>
<Storyboard x:Key="OnLoaded"/>
</Grid.Resources>
<Button Content="Hola" Background="{StaticResource Hola}" />
I try to binding StaticResource's ResourceKey to some string property
such as
<Button Content="Hola" Background="{StaticResource {Binding
Path=Content}}" />

But I get an exception whcih said that
"A Binding cannot be set on Resource Key property of type
StaticResourceExtension"

Why I can't do that?
And is there any other way to achieve the same result?

Thanks

BR,
HolaMan