Ideas on easiest way to do A/B testing with multiple contacts on a business

We're a B2B company and sometimes do A/B testing with offers to our customers. However, we can't use the "random sample" functionality as we send these emails to all the contacts in a business and don't want to risk sending both offers to the same business. My workaround is to manually pull a list from our CRM, randomize the account numbers, and split the randomized list. I then send offer A to the first list and B to the second. 

This seems like the most straightforward solution but I was wondering if anyone had any suggestions on a more automated way of doing this in Marketo?