Sample Slot Background

Hi all.

It's not in the maxscript help and the listender doesn't print it either so I'm stuck!

Does anyone know where i can find the scripting to enable the Sample Slot Background in a material?

For instance

meditMaterials[1] = VrayMtl ()
meditMaterials[1].Diffuse = color 250 250 250
meditMaterials[1].sample_slot_Background = on

The third line obviously doesn't work, but it's to give you the idea that I'd like the 'coloured cheqeured background' to be on on a material.

Cheers