Trying to get a steer on how to extract a list from a worksheet based om comparsion of criteria

[StillDontGetIt]

I have a very long worksheet full of transaction. All transactions have a unique email attached. There should be an 'in' and 'out' transaction for all email addresses. I need some help on working out how to create a query(?) process (?) magic wizardry to automate the procces as there are over 8000 entries in the worksheet.

Any tips on general approach, tutorials, previous posts, any help at all appreciated.

Thanks in advance.