Using changeSet and the selectedRow.index to update a table record

I must be overcomplicating this. I've searched for a simple solution and example to just update a cell that's been changed, on blur.
Can someone please explain a more simple approach to this.
Note: The table is a data set from a number of tables joined.

Instead of using changeSet, you can try to get the updated data from recordUpdates with supplierVariantsTable.recordUpdates[supplierVariantsTable.recordUpdates.length - 1]. This way you don't have to use selectedRow.index.