T3d 1.1 - Passing a custom value to a shader?

Hello,

I have been working on shaders in T3D for some time now, and I seem to have gotten stuck with what I thought would be a fairly simple task.

What I want to do is pass a value (an XYZ position, so, a Point3F?) from script to a shader, and be able to update this value dynamically. So, for example: myShader.customPosition = "X Y Z".

I understand that to do this I need to create a custom shader constant, which I believe I have done. I have used these three resources:

http://www.garagegames.com/community/resources/view/19161/1

http://www.garagegames.com/community/forums/viewthread/117615

http://www.garagegames.com/community/blogs/view/15211

They all seemed to make sense, and compiled perfectly. However, I don't know how to access my custom value in the shader itself.

It seems that in older versions of the engine, this code was used:

//Script Controlled Variables  
    GFX->setPixelShaderConstF( PC_USERDEF1, (float*)&mMaterial->collisionPos[stageNum], 1 );

Which uses the PC_USERDEF1 register. This makes sense, since I can then use:

uniform float3 collisionPos : register(PC_USERDEF1)

in my shader to access the value.

However, in T3D 1.1, that code changes to:

if ( handles->mCollisionPos->isValid() ){  
	 shaderConsts->setSafe( handles->mCollisionPos, mMaterial->collisionPos[stageNum]); 

	}

This doesn't seem to use a register? So I am confused as to how to access this value from the shader, and use it? I must be missing something obvious here, surely passing a custom value to a shader is a fairly common thing to want to do?

Thanks for any advice!