What I am trying to do I think is simple and what I have works but takes along time - any advice on a faster way would be grea

I have a bunch of data and I it is all dated - I set up in the last column and get a value that is "mmyyyy", but each file may have more than one moths worth of data so I copy and sort it and use the code below to delete the duplicates so that in the end I get a list of all the unique "mmyyyy" values there are. Then I take that and sort and send out to new files the origional data based on date

Sub GetFields112(
Application.Calculation = xlCalculationManua
Dim lastrow As Long, r As Lon
lastrow = ActiveSheet.UsedRange.Rows.Coun
For r = lastrow To 1 Step -
If Cells(r, 17).Value = Cells(r + 1, 17) Then Rows(r).Delet
Next
Application.Calculation = xlCalculationAutomati
End Su

What I need is a faster way to do this since a file may have many thousands of entries, is there a way to basically say, look in column "R" find all the unique values and then but them in column "S" starting in row one and listing them down

Any help would be great, what I have works but takes about 10 minutes to run, and I am looking for a shorter way to do it

Thanks

Jim