Finding the latest transaction date by list of unique customer ID

Hi,

I've been sleeping on it for almost a week, unable to find solution..
I am automating transaction dates' record. As per below, in Column A I have unique customer ID; in Column B I have transaction date; and in column C must appear last transaction date.

(A) (B) (C)
(Cust ID) (Transaction Date) (Last Transaction Date)
(1) 1234 01/12/2011 New Customer
(2) 1235 02/12/2011 New Customer
(3) 1236 03/12/2011 New Customer
(4) 1237 04/12/2011 New Customer
(5) 1234 05/12/2011 01/12/2011
(6) 1235 06/12/2011 02/12/2011
(7) 1234 07/12/2011 05/12/2011
(8) 1236 08/12/2011 03/12/2011
(9) 1235 09/12/2011 06/12/2011
(10) 1236 09/12/2011 08/12/2011


Need help to create formula in Column C that meet following objectives:
- if new cust ID, "New Customer" to appear
- for existing customer, last transaction date will appear.

Thank you in advance.

Try this:

=IF(COUNTIF(B$2:B2, B2)>1, LOOKUP(2, 1/(B$1:B1=B2), C$1:C1), "New customer")

B column is ID
C column are dates

The following formula works for me:

=IF(B1=MIN(INDEX(IF($A$1:$A$10=A1,$B$1:$B$10),0)),"New customer",MIN(INDEX(IF($A$1:$A$10=A1,$B$1:$B$10),0)))

This is an array formula, so you must enter it with Ctrl-Shift-Enter, not just enter.

Dear Zbor, Andrew-R and DILIPandey,

I really appreciate your help. All proposed solutions works well for my purpose.
I added =IF(C12<>0, IF(COUNTIF(C$2:C12, C12)>1, LOOKUP(2, 1/(C$1:C11=C12), D$1:D11), "New customer"),"-") into Zbor's solution to make the template look neater for future data entry.
Thank you all sifus, I will forward this template to all my 6 branch offices and they will start using it in five hours..
Happy New Year.