Group Companies and Identify the ones that have buyer and seller

See attached. I have the company name numbered off in sequence but I am trying to group the same company together and then identify the companies that have BOTH a Buyer and Seller transaction. I was thinking of writing a formula next to it that might be able to identify the group of same company and then identify if out of that group it has both buyer and seller and put a "1" and if not then a "2" and later i can filter to display the "1". Can anyone help with this or propose an easier method please????

Thanks,