Returning Unmatched items from a single table

[GaryB]

I don't play around much with Access, so I apologise if this is blindingly obvious!

I have a file of 120000 lines of data (and growing) which contains details of incoming dataflows (reference, type, date & time received), and hopefully the responses sent (reference, type, date and time sent)
A type A flow comes in and a type B flow, quoting the same reference, is sent back in acknowledgment, within 3 working days. What do I need to do to get a report of the type A flows that have either not had a type B sent back, or have had one but more than 3 working days later. I can produce a report of the matching ones, but cannot workout the inverse.

Many Thanks

GaryB

 

[Joe4]

Can you post a small snippet of sample data, showing the important fields and their values (type flows, dates, etc)?
And maybe the SQL code of your query that works (switch your Query to SQL View and copy and paste code here).