AutoFill of Dynamic Range

I'm trying to convert the static value of "X372:BV372" in line 1 on the screenshot into a dynamic range based on last row, but I'm getting an "AutoFill method of Range class failed" with my modifed syntax in line 2 on the screenshot..

Sub Macro5()
    With Sheets("Data03")
        lrow = .Range("A" & Rows.Count).End(xlUp).row
        .Range("X" & lrow + 1).Formula = "=SUM(X3:X" & lrow & ")"
        'Selection.AutoFill Destination:=Range("X372:BV372"), Type:=xlFillDefault <---- Recorded with the Excel Macro recorder
        Selection.AutoFill Destination:=Range("X" & lrow + 1 & ":BV" & lrow + 1), Type:=xlFillDefault <---- My modified syntax that errors out
    End With
End Sub