WPF PixelShaders: How to create a Temporary Register dependency property?

Question

Hi,

I've run out of the 8 possible constant registers in a wpf pixelshader effect. I need access to temporary registers, which I believe are available 6 on a DX 8.1 level gfx cards.

Question is: How to create a temporary register dependency property in C# code?

Constant registers are created like this:

 public static readonly DependencyProperty L1Property = DependencyProperty.Register(
      "ConstantReg0", typeof(double), typeof(MyEffect),
       new UIPropertyMetadata(0.0, PixelShaderConstantCallback(0)));

But there is no PixelShaderTemporaryCallback...?!