Your question is a little cryptic, Marie...
I assume your app has code that sorts the contents of a DataWindow when the user clicks on a column heading text label, and that, in your example, you click on either the Vendor No. or Description column heading and result after sorting shows the rows in a different order (as evidenced by the order number). Correct?
When you sort on the values contained in a single column and there are multiple rows containing the same value in that column, then this can happen because there are no additional conditions that will enforce the relative order of the rows to be "preserved". The DataWindow is doing exactly what you requested it do and nothing more. You're assuming it's going to do something you haven't told it to do.
If you want the sort to take into account additional columns you'll have to either use the PB Sort dialog window or enhance the column-heading-click/sort user interface to take multiple columns into consideration.
Regards, John