VBA How to check for duplicate values against existing list and add only unique instances from new list - excel

Question

I have three worksheets with consistent headers, but the # of columns vary:
Active List
Current List
New List
I need to compare column A from "New List" against Column B from "Active List" for duplicate instances.
I want to load only the unique instances from column A starting at row 2 along with the associated cells in Column B on my "New List" beneath the last, populated row of my "Active List" worksheet in columns B & C.
To do this, I have tried utilizing the Scripting Dictionary, but I receive Run Time Error 1004 on my object range in the following line of code:
Dict.Add Key:=NL.Range(i, "A").Value, Item:=vbNullString
Here is the full code which I mimicked from question #55499372 on StackOverflow:
Sub load_new()
Dim LastRow As Long
Dim i As Long
Dim Dict As Scripting.Dictionary
Set Dict = New Scripting.Dictionary
Dim CL As Worksheet
Set CL = ThisWorkbook.Worksheets("CURRENT LIST")
Dim NL As Worksheet
Set NL = ThisWorkbook.Worksheets("NEW LIST")
Dim AL As Worksheet
Set AL = ThisWorkbook.Worksheets("ACTIVE LIST")
'Retrieves the last row of column A
With NL
LastRow = .Cells(.Rows.Count, 1).End(xlUp).Row
End With
For i = 2 To LastRow
Dict.Add Key:=NL.Range(i, 1).Value, Item:=vbNullString
Next i
'Retrieves the last row of column B
With AL
LastRow = .Cells(.Rows.Count, 2).End(xlUp).Row
End With
For i = 2 To LastRow
If Not Dict.Exists(AL.Range(i, 2).Value) Then
End If
Next i
End Sub

Answer 1

Load the dictionary with keys from Active List column B, then scan the New List column A checking if key does not exist.
Option Explicit
Sub load_new()
Dim wsCL As Worksheet, wsNL As Worksheet, wsAL As Worksheet
Dim LastRowAL As Long, LastRowNL As Long
Dim i As Long, n As Long, key As String
Dim Dict As Scripting.dictionary
Set Dict = New Scripting.dictionary
With ThisWorkbook
'Set wsCL = .Sheets("CURRENT LIST")
Set wsNL = .Sheets("NEW LIST")
Set wsAL = .Sheets("ACTIVE LIST")
End With
' Active List
With wsAL
LastRowAL = .Cells(.Rows.Count, "B").End(xlUp).Row
For i = 2 To LastRowAL
key = Trim(.Cells(i, "B"))
If Len(key) > 0 Then
Dict.Add key, i
End If
Next i
End With
' New List
With wsNL
LastRowNL = .Cells(.Rows.Count, "A").End(xlUp).Row
For i = 2 To LastRowNL
key = Trim(.Cells(i, "A"))
If Not Dict.Exists(key) Then
LastRowAL = LastRowAL + 1
wsAL.Cells(LastRowAL, "B") = key
wsAL.Cells(LastRowAL, "C") = .Cells(i, "B")
n = n + 1
End If
Next i
End With
MsgBox n & " rows added to " & wsAL.Name
End Sub