Update Records which contains duplicate Comma Separated data.

Hi,
Can we remove duplicate values from one cell. These values are comma separated.
CustomerId
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,6
I want to update this field so that i can have only,
CustomerId
5,6
Can some one please help? how can i solve this problem.
Thanks.