Change a parameter of a shader

[Matt'.]

Hi, I want just to change the value of DepthBias by Lua

So here, I have defined a parameter which I named parameter1, and the rest is just for replace.fx

texture gTexture;
float parameter1;

technique TexReplace
{
    pass P0
    {
		DepthBias =	parameter1;
        Texture[0] = gTexture;
    }
}

And now, we gonna go to Lua File : (the shader is working etc...)

dxSetShaderValue(shader, "parameter1", -0.0006)

So here, it doesn't work, DepthBias doesn't take the value of parameter1 as I wrote in the .fx file  !

Any help please?