Check if unique identifier is present in "new data", if not, add entries to "historical data" sheet? - vba

Question

I've got data with a unique ID number in one column. This is pasted into a "Raw Data" sheet by the user.
Then, I've got macros that manipulate the "Raw Data", including archiving some of it on a "archival" worksheet which includes the ID numbers.
I want to run a check to see if there are any "new" ID numbers in the "Raw Data", and if so add a new row with some of the data including the ID number to the "archival" sheet.
I've googled and checked here. It looks like I want to use a Collection? Never encountered this so far, not sure where to start.
Sorry that this isn't the most well structured question, and that it doesn't include any code. Not sure how to get started.
It should be noted that this reconciliation only needs to go one way -- I don't need to delete "old" unique IDs from the "archival" sheet.
Thanks!

Answer 1

If you specifically want to use collections, over Range.Find, you can do so like this.
Although handling errors this way in VBA is best to avoid most times, for iterating over collections, it can result in faster and often less verbose code.
I have used named ranges for a Rawdata and Archive worksheet tabs, so you will need to adapt this to your own situation. What this does is use collections to store unique items already in Archive, and compare these against items in Rawdata - when a new (unique) item is found in Rawdata that is not already in Archive, it is added to the sheet (and collection).
Sub IDcollection()
Dim IDcoll As New Collection
Dim cells, Rng, Rng_a As Range
Set Rng = Worksheets("Rawdata").Range("IDRANGE")
Set Rng_a = Worksheets("Archive").Range("IDRANGE_A")
'IDRANGE looks like string IDs 'abc', 'ab1',etc
'get unique IDs already in ARCH sheet via named range
On Error Resume Next 'includes only unique items
For Each cells In Rng_a.cells
IDcoll.Add cells.Text, cells.Text
'use the IDs as the KEY in the VBA Collection
Next cells
'check for unique items not in Archive, but in Rawdata (i.e. new items)
On Error Resume Next
For Each cells In Rng
IDcoll.Item cells.Text
If Err.Number <> 0 Then
IDcoll.Add cells.Text, cells.Text
LastRow = Rng_a.Rows(Rows.Count).End(xlUp).Row + 1
Rng_a(LastRow).Value = cells.Text
Err.Clear
End If
Next
End Sub
Just stick this in a module in your VBA for your worksheet, set up some named ranges as above, populated with dummy data.