Macro to help remove duplicate rows in excel spreadsheet

Sub duplicate_flg()
' Use to remove duplicates
' Check for duplicates based on columns colx and coly. Customize below.
' flag them in column colflg
' Rowcounts based on column - colx
' ******************************************************
' NEEDs a sorted sheet and assumes a header
' Runs on the active sheet in the active workbook
' ******************************************************

colx = 1
coly = 2
colflg = 3
Cells(1, colflg) = "Is Duplicate?"

lastrowcnt = Cells(Cells.Rows.Count, colx).End(xlUp).Row
'lastrowcnt = 7
ActiveWorkbook.Activate
Set ws = ActiveWorkbook.ActiveSheet

' header assumed. starts from row 2
For i = 2 To lastrowcnt
    If ws.Cells(i, colx) = ws.Cells(i + 1, colx) And _
        ws.Cells(i, coly) = ws.Cells(i + 1, coly) Then
        ws.Cells(i + 1, colflg) = "Y"
    End If
Next i

End Sub