Sub SumColJ()
Dim srcSht As Worksheet: Set srcSht = Sheets("Sheet1")
Dim destSht As Worksheet: Set destSht = Sheets("Sheet2")
Dim LR As Long: LR = srcSht.Range("J" & Rows.Count).End(xlUp).Row
Dim rng As Range: Set rng = destSht.Range("A1")
rng = Application.WorksheetFunction.Sum(srcSht.Range("J3:J" & LR))
End Sub