I have got a mental blank and cant thing how the code goes and i am no near excell at the moment but the way would be to preform a lookup, vlookup i think, and set it to look up all records "after" 28 days ago. You will have to calculate 28 days or you can just manually enter it. To auto calc 28 days it will have to be =now(sum-28) i think thats it any way, i will have a look later if you have not solved it by then...
You need to get it to show records after a given date, the given date would be 28 days, i am sure it can be done without macros too.