Formula to highlight values based on other cells with the same value

[srpattrick]

Hi,

I have 2 columns containing Order Numbers and the transaction date and time.

I need to identify orders where the Transaction date and time are different to the same order Number:

Order Date & Time
23 01/01/15 10:57am
23 01/01/15 10:57am
27 02/01/15 09:00am
27 02/01/15 11:00am
27 02/01/15 09:00am

It should therefore highlight Order 27 where the Time is different to the others in the same order (also need to highlight when the dates are different too).
Any help would be appreciated

[Kamboj]

You can use conditional formatting | highlight Cell Rules | Duplicate values and then select Unique/ Duplicate to highlight.

[srpattrick]

Hi,
This does not highlight values based on the order ID but only highlights unique values.
I need to verify that all transaction dates and times are identical for each individual order number....
Any help would be great.
My assumption would be the requirement of IF function but I am no expert