Duplicate leads

We attend trade shows and are always getting new leads. However, we can get multiple leads from the same company, but we only want to import one per company. We currently wash the data in Excel to remove dups. However, the company my already exist in or leads DB and we do not want to add another lead from the same company.

Zoho only allows no dups for email when importing. Is there a way to use the company name to avoid duplicates when importing into leads?

Thanks

Tony