float Progress;

texture Input1;
sampler Input1Sampler = sampler_state
{
	Texture = <Input1>;
};
texture Input2;
sampler Input2Sampler = sampler_state
{
	Texture = <Input2>;
};


float4 Blinds(float2 uv)
{
	if (frac(uv.y * 5.0f) < Progress)
	{
		return (tex2D(Input2Sampler, uv));
	}
	else
	{
		return (tex2D(Input1Sampler, uv));
	}
}

//--------------------------------------------------------------------------------------
// Pixel Shader
//--------------------------------------------------------------------------------------
float4 main(float2 uv : TEXCOORD) : COLOR
{
	return (Blinds(uv));
}


technique BlindsTransition
{
	pass BlindsTransition
	{
		VertexShader = null;
		PixelShader = compile ps_2_0 main();
	}
}

m_effect.Technique = "BlindsTransition";
m_effect.SetValue<float>("Progress", 1.0f);
m_effect.SetTexture("Input1", m_screenTexture1.DXTexture);
m_effect.SetTexture("Input2", m_screenTexture2.DXTexture);
m_effect.CommitChanges();

m_effect.Begin();
m_effect.BeginPass(0);

m_bottomQuad.Render(device);

m_effect.EndPass();
m_effect.End();

SlimDX.Direct3D9.Direct3D9Exception occurred
  Message="D3DERR_INVALIDCALL: Invalid call (-2005530516)"
  Source="SlimDX"
  StackTrace:
       at SlimDX.Result.Throw[T](Object dataKey, Object dataValue)
       at SlimDX.Result.Record[T](Int32 hr, Boolean failed, Object dataKey, Object dataValue)
       at SlimDX.Direct3D9.Effect.set_Technique(EffectHandle value)
       at DXSplitScreen.Render(Device device) in ...Engine\DXSplitScreen.cs:line 252
       at DXRenderer.RenderMiddle() in ...Rendering\DXRenderer.cs:line 451
       at DXRenderer.Render() in ...Rendering\DXRenderer.cs:line 186
  InnerException: 

The strange thing is if I remove the line

m_effect.Technique = "BlindsTransition";

then I can get the two textures fading into each other by setting the "Progress" variable. Adding that line back in and it fails. Why?

Nevermind, I was actually loading the wrong shader!