Ok, here's what I've got, though it's not having the desired effect. It seems to control the overall reflectivity, and to a small degree reflectivity away from the centre - but not in terms of pitching the reflectivity more towards the glancing, rather than facing, angle.

Have I set it up correctly?

thanks,

gubar.
Edit: Looking at my network I notice that, when I drag and drop the ramp to the reflectivity in the atribute editor, it attatches the alpha out to the reflectivity; if I open up the connections, I have the option of connecting the out colour to the reflected colour, but not the reflectivity itself.