Hi, vipulhumein,

it doesn't work after applying in this workbook
Where´s the code you used? I can´t look into your computer I´m afraid.

The code assumes that you open the workbooks in the same instance of Excel, not in different ones.
'This Workbook
Option Explicit

Private Sub Workbook_Open()
EF912816
End Sub
'Code Module
Option Explicit

Sub EF912816()
Dim wb As Workbook
Dim wbONE As Workbook
Dim wbTWO As Workbook

Const cstrWB_ONE As String = "Raw Data.xlsm"      'alter to suit name and extension
Const cstrWB_TWO As String = "Sample.xlsx"        'like above
Const cstrPATH As String = "C:\HaHoBe\Downloads\" 'alter the path to the workbooks, I
                                                  'assumed they both are located in the same place

For Each wb In Workbooks
  If wb.Name = cstrWB_ONE Then
    Set wbONE = wb
  End If
  If wb.Name = cstrWB_TWO Then
    Set wbTWO = wb
  End If
Next wb

If wbONE Is Nothing Then
  Set wbONE = Workbooks.Open(cstrPATH & cstrWB_ONE)
End If

If wbTWO Is Nothing Then
  Set wbTWO = Workbooks.Open(cstrPATH & cstrWB_TWO)
End If

End Sub
Ciao,
Holger