Fast merging duplicates in excel using VBA - vba

Question

I created a macro in Excel to mergue duplicated rows:
The idea is that if 2 rows or more have the same A B C columns, I mergue their D columns removing ABC duplicates.
I need to do this, but checking more colums.
My macro looks like this:
processingRow = 2
Do Until Cells(processingRow, 1).Value = ""
i = processingRow + 1
Do Until Cells(i, 1).Value = ""
If Cells(processingRow, 8) = Cells(i, 8) And _
Cells(processingRow, 12) = Cells(i, 12) And _
Cells(processingRow, 7) = Cells(i, 7) And _
Cells(processingRow, 6) = Cells(i, 6) And _
Cells(processingRow, 5) = Cells(i, 5) And _
Cells(processingRow, 4) = Cells(i, 4) And _
Cells(processingRow, 3) = Cells(i, 3) And _
Cells(processingRow, 2) = Cells(i, 2) And _
Cells(processingRow, 1) = Cells(i, 1) Then
If Cells(i, 14) <> "" Then
Cells(processingRow, 14) = Cells(processingRow, 14) & "," & Cells(i, 14)
End If
Rows(i).Delete
End If
i = i + 1
Loop
processingRow = processingRow + 1
Loop
When running the macro with 500 rows, it takes a while, but its still reasonable. But I need to run this macro in a excel with more than 2500 rows, and it takes so much time that its not practical anymore.
This is my first macro in excel using VBA, so I was wondering if there is a faster way to process rows/cells, since accessing them individually seems extremelly slow.
Any ideas?

Answer 1

EDITED: I missed that you weren't checking every column to determine what was a duplicate. This should be closer now:
Sub Tester()
Dim rngCheck As Range, rw As Range
Dim dict As Object, k As String, rwDup As Range
Dim rngDel As Range, tmp
Set dict = CreateObject("scripting.dictionary")
With ActiveSheet
Set rngCheck = .Range(.Cells(2, 1), _
.Cells(Rows.Count, 1).End(xlUp)).Resize(, 14)
End With
For Each rw In rngCheck.Rows
k = RowKey(rw)
If dict.exists(k) Then
Set rwDup = dict(k)
tmp = rw.Cells(14).Value
If Len(tmp) > 0 Then
rwDup.Cells(14).Value = rwDup.Cells(14).Value & "," & tmp
End If
If rngDel Is Nothing Then
Set rngDel = rw
Else
Set rngDel = Application.Union(rngDel, rw)
End If
Else
dict.Add k, rw
End If
Next rw
If Not rngDel Is Nothing Then rngDel.EntireRow.Delete
End Sub
'create a "key" for the row by joining all columns to be checked
Function RowKey(rw As Range) As String
Dim arr, x As Long, sep As String, rv As String
arr = Array(1, 2, 3, 4, 5, 6, 7, 8, 12)
For x = LBound(arr) To UBound(arr)
rv = rv & sep & rw.Cells(arr(x)).Value
sep = Chr(0)
Next x
RowKey = rv
End Function