COL unique (CustomerID) plus COL unique (COUNT) inside CustomerID

Hello to all,

after a period of silence from Debian, Courier, PHP and PostgreSQL I  am
half back and running into a problem...  :-/

I need a table with an UNIQUE CustomerID which is working fine...

...BUT I need also a second column with a count, which  must  be  UNIQUE
inside the CustomerID.

In clear this:

    CustID       Count
         1           1
         1           2
         1           3

         2           1
         2           2

         3           1
         3           2
         3           3
         ...

How to do this?

Thanks in avance

--
Michelle Konzack        ITSystems
GNU/Linux Developer     0033-6-61925193