Sorting Dynamic Table

Hi -

I am using LiveCycle Designer ES 8.2 to design a fairly simple form. I have a table set up with repeating rows. All data is user entered. I would like the user to be able to sort the table (list) based on last name. I have reviewed other posts, but must be missing something. I tried a button with this, but it 's not working: 

SubformSort.sort(

this, _Row1, "NameLast",

asc);

I am very new to LiveCycle and greatly appreciate any advice you can provide.

Thanks!