a simple example

Code:
texture TargetMap; // bmap_process bmSrc
texture mtlSkin1; // 32bit mask

sampler ColorSampler = sampler_state { Texture = <TargetMap>; };
sampler MaskSampler = sampler_state { Texture = <mtlSkin1>; };

float4 PS ( in float2 inTex: TEXCOORD0 ) : COLOR0
{
	return float4 ( tex2D ( ColorSampler, inTex ).rgb, tex2D ( MaskSampler, inTex ).a );
}

technique
{
	pass p0
	{
		VertexShader = null;
		PixelShader  = compile ps_1_1 PS();
	}
}


Salud!