Copying Unique Records to Another Sheet.

I think you are barking up the wrong tree by wanting to use VBScript Dictionaries. It's a great way to get a list of unique items in a single column list, but won't help you improve the speed of copying data from a multi-column table from one worksheet to another.

Instead, consider adding a COUNTIFS formula to Sheet2 that tests whether there is a match on Sheet1. Sort Sheet2 by the results of this formula, then do a single copy & paste to Sheet3. Your question title implied copying values that weren't found on Sheet1 over to Sheet3, but the body of the question suggested the opposite.

The slow part in moving data from one worksheet to another is looping through the rows and moving them one at a time. The sorting operation has been optimized in Excel, and will be very fast. So merely by adding a sort step, you should get a large improvement in speed.

If you don't need to copy over the formatting, it is faster to use the .Value property of the sorted range to transfer just the values. I have been told, but cannot verify from personal experience, that the .Value2 property is even faster than .Value.

Dim rgCopy as Range
Set rgCopy = xxxxxxx
Worksheets("Sheet3").Range(someCell).Resize(rgCopy.Rows.Count, rgCopy.Columns.Count).Value = rgCopy.Value

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Thanks for your efforts . I have attached a sample with this comment . I request to see the sample and request you to provide give me  the best code to execute them in fastest manner .  

It should basically compare the two sheets ( sheet1 and sheet2 ) . The unmatched records available in sheet2 ( highlighted for the reference ) should be copied to sheet3 .
Sample.xlsx

Sub MoveDupes()
Application.ScreenUpdating = False
With ThisWorkbook
    FindDupes .Worksheets("Sheet1"), .Worksheets("Sheet2"), .Worksheets("Sheet3")
End With
End Sub

Sub FindDupes(ws1 As Worksheet, ws2 As Worksheet, wsDest As Worksheet)
'Look for records in ws2 that isn't in ws1. Copy those rows to wsDest.
Dim frmla As String
Dim rgCopy As Range, rg1 As Range, rg2 As Range, rgTest As Range
Dim n As Long, nCols As Long, nRows As Long
Set rg2 = ws2.Range("A1").CurrentRegion
nCols = rg2.Columns.Count
nRows = rg2.Rows.Count
Set rg2 = Range(rg2.Cells(2, 1), rg2.Cells(nRows, nCols))

Set rg1 = ws1.UsedRange
Set rg1 = Range(rg1.Cells(2, 1), rg1.Cells(rg1.Rows.Count, nCols))
Set rgTest = rg2.Columns(nCols + 1)
frmla = FormulaBuilder(rg1, rg2)
rgTest.Cells(1).Formula = frmla
rgTest.FillDown
rgTest.Formula = rgTest.Value
Sorter rgTest
n = Application.CountIf(rgTest, "Unique")
If n > 0 Then
    Set rgCopy = Range(rg2.Cells(1, 1), rg2.Cells(n, nCols))
    wsDest.Cells(2, 1).Resize(n, nCols).Value = rgCopy.Value
End If
rgTest.EntireColumn.Delete
End Sub

Function FormulaBuilder(rg1 As Range, rg2 As Range)
Dim addr1 As String, addr2 As String, frmla As String
Dim i As Long, nCols As Long
nCols = rg2.Columns.Count
frmla = "=IF(COUNTIFS("
addr1 = "'" & rg1.Worksheet.Name & "'!"
For i = 1 To nCols
    frmla = frmla & addr1 & rg1.Columns(i).Address(ReferenceStyle:=xlR1C1) & ",""="" &RC" & i & ","
Next
FormulaBuilder = Left(frmla, Len(frmla) - 1) & ")=0,""Unique"","""")"
End Function

Sub Sorter(SortColumn As Range)
'Sort target worksheet by SortColumn in alphabetical order
Dim SortRange As Range
Set SortRange = SortColumn.CurrentRegion
With SortColumn.Worksheet
    .Sort.SortFields.Clear
    .Sort.SortFields.Add2 Key:=SortColumn, SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    With .Sort
        .SetRange SortRange
        .Header = xlYes
        .MatchCase = False
        .Orientation = xlTopToBottom
        .SortMethod = xlPinYin
        .Apply
    End With
End With
End Sub

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SampleQ29143857.xlsm

It works perfectly . I have changed  selection of the columns and rows as I needed to add labels and buttons . I have attached the sample below . I tried to run the code ,  the sheets does not any unique records , still I see records are shown in sheet3  and also I don't want to  see " Unique ".  One more thing , existing data in sheet3 should be deleted , when next operation is performed . Again thanks for your effort .
SampleQ29143857.xlsm

Nailed it .

How is the speed on your real problem?

It really does the job but takes literally around 3 to 4 min to execute . It needs to compare around 3000 rows each time. I have one suggestion , if compare just three columns D,E,F ( from sheet 1 ) and B,C,D ( from sheet 2 ) . Based on results we can copy the select the record and copy it to sheet3. Can It increase the execution time.

Yeah . Now it executes within seconds . Thanks .

Hi , I face one problem . The code executes in exceptionally well in my Computer . I am using Excel 2019 . When I tried running this function in my colleague computer which is using  Excel 2010 . It shows object error during Execution. Is there any problem , when executed in older versions.

Thanks . It Works