How to use Particle System custom data with Amplify?

Hello, I'm trying to randomly change attributes of a particle system texture, in this example, it's simply the UV size
But, I seem to not be able to do it using custom data
Image: http://www.antigengames.com/mt-content/ ... coords.jpg

Can this be done? Thanks
But, I seem to not be able to do it using custom data
Image: http://www.antigengames.com/mt-content/ ... coords.jpg

Can this be done? Thanks