Sort with numbers

Hello,

I have a list of 12 products and need to give to my client a way to decide which product goes to position 5 and position 9. I don't think there is a way to do that, so I thought of giving her a select field (id="position") with options from 1 to 12 and sort using this field. I then change the template based on this field's value. The problem is, as far as I understand, that 'sort' => 'position' treats the values as strings instead of numbers which doesn't give the desired output. How can work around this behaviour?