End user disc space upgrade

Hi,

In my support settings, I've allowed for my users to access 1 GB of storage for their monthly fee.

I've made all sorts of Ecommerce tools available to users and am hoping they'll use up their 1GB quickly so they will want to purchase the bulk upgrades I am offering.

But how will they (and I) know when they are about to exceed their storage capacity?

It would be great if I could configure an email message with a discount voucher offer (voucherpress) to be
automatically sent out.

Thanks,
Derek