Design Studio - Data Source - Find Maximum Value

Hi Guys,

I have a data source with 2 columns like:

Invoice Number          Amount

I001                              500

I002                              600

I003                              300

I want to get the maximum amount among all the invoices which is 600 in this case. Can some one tell me how to get the maximum value through script in design studio. I want to display this value in a text field.

Thanks and best regards.

Fahad