Formula to assign a visit number

Hi Everyone,

Can someone help me please,
I am trying to assign a visit number according to the date for each visitor based on their unique number.

Visitor_ID....Visit_Date
1................July 1/2013
1................July 3/2013
1................Aug 2/2013
2................july 10/2013
2................July 15/2013

I would like to add a column to assign a visit number:

Visitor_ID....Visit_Date...........Visit_number
1................July 1/2013.........1
1................July 3/2013.........2
1................Aug 2/2013.........3
2................july 10/2013........1
2................July 15/2013........2

I really appreciate your help,

Thanks,
Amanco

Thank you, it is working!

can I ask one more question please,
now how can I extract or advance filter only the last visit based on the visit ID and other columns in the sheet, for example:

Visitor_ID....Visit_Date...........Visit_number....Data
1................July 1/2013.........1....................Red
1................July 3/2013.........2....................Blue
1................Aug 2/2013.........3....................Orange
2................july 10/2013........1....................Red
2................July 15/2013........2....................Pink

To:
Visitor_ID....Visit_Date...........Visit_number....Data
1................Aug 2/2013.........3....................Orange
2................July 15/2013........2....................Pink

Thanks again,
Amanco

Hi Amanco

First sort visit_Number in descending order. Next go to advanced filter, click on Unique Records and then click ok. You will find below results:

Visitor_ID....Visit_Date...........Visit_number....Data
1................Aug 2/2013.........3....................Orange
2................July 15/2013........2....................Pink

Thanks
Shyam