You would need to utilize the regular (retail) member login and then set up a customer group and price category for wholesalers. If you are already using the actual wholesale side of the site, you would need to have the customers re-register on the regular side of the site. Then, once you approve them to be wholesalers, you would add them to the 'Wholesale' cgroup which would have the price category for wholesalers so they could receive their wholesale pricing.