Generic Child Variants with 'product_available_date'

[OriyanJ]

I'm using Generic Child Variant custom field to let client choose a product's date. I came up with 2 things I'm trying to solve -

1. I don't want to show past dates. Right now, VirtueMart will extract every child available. Where should I start looking in order to temper with the drop-down items?
2. I want to change to format dates are being displayed, if that somehow related to the 1st question, I can figure it out once I'm there. But if there's a way to do that other-wise, I could use the direction.