Functions- Spreadsheet That Contains Data

I have a MS Excel spreadsheet that contains data as such:

A1 - 01T2001
A2 - 02T7001
A3 - 01T2001
A4 - 99T1001
A5 - 99T1001
A6 - 02T7001
A7 - 93T0120
.
.
.
A9999999 - 02T7001
A1000000 - 93T0120

There are duplicates in the data. Excel functions to identify the duplicates. I received a VB code from a friend but there are over 1 million rows on my spreadsheet, and it took more than a day but the scribe is still running. I want to try using a COUNTIF or FIND function to see if it couldspeed upthe process.

The code I receive from the friend is

Option Explicit

Public Sub Main()

Range("A1").Select
Dim strColumn As String
strColumn = InputBox("Please enter the column that contains the duplicates.", , "A")
If strColumn = "" Then Exit Sub

Range(strColumn & "1").Select
ActiveCell.Sort Key1:=Range(strColumn & "1"), Order1:=xlAscending
Do
If ActiveCell.Value = ActiveCell.Offset(1, 0).Value Then
Rows(ActiveCell.Row).Delete Shift:=xlUp
Else
ActiveCell.Offset(1, 0).Select
End If
Loop Until ActiveCell.Value = ""
Range(strColumn & "1").Select
End Sub