Detect Row Changed event in a grid and make changes to the header

On screen "Pick, Pack, and Ship", (SO302020) I am trying to make some changes, but it is an odd screen so any ideas would be welcome. I have managed to make some changes and I am spending a lot of time in the debugger trying to understand what I can do but I haven't got that far yet.

I have been working with methods and events like:

SOShipLineSplit_RowSelecting

SOShipLineSplit_RowSelected

SOShipLineSplit_LineNbr_FieldSelecting

These don't fire when I would expect. They don't fire when I click on the grid. Perhaps this is because the grid is is not editable. I don't see how to change this.

Basically what I ideally want is to detect when a row is selected or clicked on and then run code populate the Scan field with the Inventory Code.

I could also do this from the header on a button or something, but when I play with events on the header and get a link to the table I can't see a selected row in there so I am stumped.

// Acuminator disable once PX1045 PXGraphCreateInstanceInEventHandlers [Justification]

PickPackShip.Host graph = PXGraph.CreateInstance<PickPackShip.Host>();

PXCache split = graph.Caches<SOShipLineSplit>();

I have tried a lot of routes so I just need some advice on how to make this work.

Many thanks.