highlight multiple occurances of a customer number

[Jules.]

Hi

I have a form that lists customer details. If those details change we keep
an old copy and use their existing customer number on a new record (Primary
key is Date of Registration field + customer number). Therefore within the
data we can have several instances of the customer number.

When this occurs i would like to have the records with more than one
occurance of a customer number be in bold and colored red.

I'd be really grateful for any ideas.

Thanks