Check for Duplications when transferring data from One Workbook to Master Workbook

Hello,

I need your help! I wanted to see if there was a way to check for duplicates before transferring data from one workbook to my master workbook. Is there a way to scan the rows of the master workbook and see if the data being transferred over is a duplicate? Here is the code I am running to copy the data to my master. Please let me know. Any suggestions will be greatly appreciated!

Sub copyFormToMaster()


Application.ScreenUpdating = False

Workbooks.Open FileName:=ThisWorkbook.Path & "\CRForm.xlsm"


Windows("CRForm.xlsm").Activate
Unload requestForm
        
        dataB = Sheets("Database").Range("B2")
        dataC = Sheets("Database").Range("C2")
        dataD = Sheets("Database").Range("D2")
        dataE = Sheets("Database").Range("E2")
        dataF = Sheets("Database").Range("F2")

        
Windows("ChangeRequestMaster.xlsm").Activate
  
Dim nextRow As Long
Dim dataSheet As Worksheet
Set dataSheet = ThisWorkbook.Worksheets("Database")

With dataSheet
nextRow = .Cells(.Rows.Count, "A").End(xlUp).Offset(1, 0).Row
        With .Cells(nextRow, "A")
            .Value = "ID" & nextRow
        End With
        .Cells(nextRow, "B").Value = dataB
        .Cells(nextRow, "C").Value = dataC
        .Cells(nextRow, "D").Value = dataD
        .Cells(nextRow, "E").Value = dataE
        .Cells(nextRow, "F").Value = dataF
 
        
End With

Windows("CRForm.xlsm").Activate
ActiveWindow.Close
Application.ScreenUpdating = True

End Sub