query list values within designer

Hello,

I'm trying to accomplish this with SharePoint 2010 Designer:

Create a layout table with as many columns as the number of distinct values of a particular field within a custom list.

Let us assume for example:

The Count of distinct Part_number would be 2 (2500 and 2533) thus I would iterate throught the value of 2 (for example by storing it in a variable) and create a table with 2 columns.

Any idea how to query the list for this?

Thank you.