There's actually no need to list out the details of every single purchase. You can simply enter "various" in the date acquired box and a sum total of the basis in the cost basis box.
If you really want to list out each purchase - that detail information is not submitted with your income tax return - after filling out the 1099-B page, (put $0 in the basis box), click "Guide me step by step", select the "my sale involves one of these uncommon situation" option, select "stock" as what you sold, and on the "Did you buy this stock?" page select "I bought this stock" and "Two or more times."
Tom Young