How can someone order 2 of the same item in different sizes?

how can someone order 2 of the same item in different sizes?

Please let me know as soon as possible. I'm nervous now and have to come up with a very fast solution if this isnt capable.

This is possible with a sub-product option applied to the size property.

Create Sub-Products Based on a Product Option

It seems to be already implemented on your '2016 Orderform 3 item' form.

If you need any further assistance, please let us know.