Macro to search column for matching value and add timestamp

Application.ScreenUpdating = False
Dim j As Long, i As Long
Dim lastRow1 As Range, lastRow2 As Range
Dim sh_1, sh_2 As Worksheet
Dim barcode As String
Dim wrkbk1 As Workbook, wrkbk2 As Workbook
Set wrkbk2 = ThisWorkbook
Set wrkbk1 = Workbooks.Open("H:\users\Scoti\Timer.xlsx")
Set sh_1 = wrkbk2.Sheets("Nucomat_Dashboard")
Set sh_2 = wrkbk1.Sheets("Times")
lastRow1 = sht_1.Range("K4:K43").End(xlDown).Rows.Count
barcode = sh_1.Cells(j, 1).Value
For j = 2 To lastRow1
With wrkbk1
lastRow2 = sh_2.UsedRange.Rows.Count
For i = 2 To lastRow2
If sh_2.Cells(i, 2).Value = barcode Then
sh_2.Cells(i, 4).Value = Format$(Now(), "yyyy-mm-dd hh:nn:ss")
End If
Next i
Next j
ActiveWorkbook.Save
ActiveWindow.Close
Application.ScreenUpdating = True
End With
End Sub