Counter for unique values

Hi Guys,

Need suggestion on the below situation..

I have a Characteristic..

Field1

100

200

300

400

100

100

Now i have to populate a count of the unique values for this field in BEx functionality.

So another field to be created which will show the result in report for above data as 4.

It should just take count of 1 even if there are duplicates whether 100 or any other value is shown as many times in data.

Please suggest how to achieve this.

Regards

Zabi