Macro Autofill to last Row (newbie here, read other posts already)

Hi all,
I am new to the forums and to VBA editing. I am trying to get a macro to autofill formulas to the last row on a sheet completed daily that pulls varying total of rows. I've read other posts requesting the same and tried applying the lastrow code but could not get it to work.

The VBA code is as follows

 ActiveCell.FormulaR1C1 = "Converts Rate"
    Range("L2").Select
    ActiveCell.FormulaR1C1 = _
        "=IF(OR(RC[-1]={""B"",""C"",""D"",""N"",""O"",""P"",""R""}),1,0)"
    Range("L2").Select
    Selection.AutoFill Destination:=Range("L2:L2000")
    Range("L2:L2000").Select
    Columns("M:M").Select
    Selection.Insert Shift:=xlToRight
    Range("M1").Select

My reference column for lastrow would be column A.

Any help would be appreciated.