Prevent duplicate copy paste in excel - vba

Question

Hi all the noob is back again. I am doing a copy paste job of data from one worksheet into another which is hidden but there is a danger that data will be duplicated if not checked against what has already been pasted. So far, what I have done is to insert a code in the worksheet I am copying to, to stop the duplication but the complication I now have is that the validation is checking every bit of data throughout the column from start to end and this is about 5000< entries. Column B has the report date which is the same for all entries belonging to the same month end. So it will have say 5000 entries with 30/1/13....another with 28/02/13 etc. Ideally, I want to only check once in Column B where the report date is entered and if the date matches to what I want to copy, then reject the entire copy paste process instead of validating each individual entry in the copy range. Here is the code I am working with. I hope I'm making sense & thank you very much for helping.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim r As Range
Dim ans As String
Const myCol As Long = 2
If Intersect(Target, Columns(myCol)) Is Nothing Then Exit Sub
Application.EnableEvents = False
For Each r In Intersect(Target, Columns(myCol))
If Application.CountIf(Columns(myCol), r.Value) > 1 Then
MsgBox (r.Value & " already exsists")
r.ClearContents
End If
Next
Application.EnableEvents = True
End Sub
thats my code including the remove duplicates but it aint working. I have tried it
Sub LoadData_toTable()
Dim ws1LRow As Long, ws2LRow As Long
Dim ws1 As Worksheet, ws2 As Worksheet
Application.ScreenUpdating = False
Set ws1 = ThisWorkbook.Sheets("RAW DATA")
Set ws2 = ThisWorkbook.Sheets("DATA INPUT")
With ws1
ws1LRow = .Cells.Find(What:="*", _
After:=.Range("A1"), _
Lookat:=xlPart, _
LookIn:=xlFormulas, _
SearchOrder:=xlByRows, _
SearchDirection:=xlPrevious, _
MatchCase:=False).Row + 1
End With
With ws2
ws2LRow = .Range("G" & .Rows.Count).End(xlUp).Row
.Range("A2:AR" & ws2LRow).Copy
ws1.Range("A" & ws1LRow).PasteSpecial xlPasteValues
Application.CutCopyMode = False
Application.ScreenUpdating = True
End With
With ws1
ws1.Range("A:A").RemoveDuplicates
End With
For Each WS In ThisWorkbook.Worksheets
For Each PT In WS.PivotTables
PT.RefreshTable
Next PT
Next WS
MsgBox "Loading month's data complete!"
End Sub

Answer 1

A very-long-calculation-time-solution would be to create an array containing only data not equal to that already in the sheet (you would have to iterate each copied element and compare to each element in the hidden sheet).
Otherwise you could format the duplicated data in some way, then iterate and remove all the formatted data except the first (which you would re-format as before). Example:
Selection.NumberFormat = "0.0 ""double""" '<--- this could be made also with colors
Selection.FormatConditions.AddUniqueValues
Selection.FormatConditions(Selection.FormatConditions.count).SetFirstPriority
Selection.FormatConditions(1).DupeUnique = xlDuplicate
ExecuteExcel4Macro "(2,1,""0.0 ""double"""")"
Selection.FormatConditions(1).StopIfTrue = False
Then inside iteration
cells(x,y).select
if counted_formatted_data = 1 then
Selection.NumberFormat = "0.0 " '<--- back to the previous formatting
else
selection.delete
end if
Of course it is better if you do this without selecting anything.