HI Mike,

Yes on NewRow and on FilterRow you can use OnCellSelect event since both object always selected as a row object. I suggest you to use OnRowSelect client side event to check the type of selected row. Here the code snippet:

function WebGrid1_OnRowSelect(controlId, tblName, rowIndex, rowEl)
{
	var WebGrid1 = ISGetObject(controlId);
	var selectedRow = WebGrid1.GetSelectedObject().ToRowObject();
	alert(selectedRow.Type);
	return true;
}

And about selecting GroupHeader it should be worked too with those code snippets. Hope this helps.

Thank you - I have that much in place.

But with CellClickAction=CellSelect, the user can arrow left/right to different CELLS within the row.  I need to know which cell is focused on/selected, not just that the NewRow is selected as a whole.

I would have expected the OnCellSelect to fire in this case, but it doesn't seem to fire for either NewRow or FilterRow.

Yes, I have checked that behavior and able to reproduce the issue here. But I'm not sure whether this is what our developer designed for WebGrid onCellSelect behavior. 
One for sure if you focus in one of cell in NewRow of FilterRow by click on it and then press TAB the onCellSelect event will be triggered. While if user using keyboard arrow buttons the cell only highlighted but not selected. I think this is the reason why onCellSelect won't be triggered for this scenario.

I suggest you to submit feature request regarding this issue, so our dev team can check the possibility or  implement new client side event that can handle your scenario.

Kind Regards,

Dicky

Thank you - how would you like me to submit this as a feature request?  TDN?

I wouldn't see why OnCellSelect wouldn't be an appropriate event, as you can check selectedobject to see what type it is, but if it'll cause conflict with existing apps, I can deal with another set of events.  I just need something that will fire consistently regardless of how the cell got focus (keyboard, mouse, click, etc).

Yes please submit it in TDN (Developer Network >> My Community Center >> Product Feedback tab).
You can add this thread link as reference so it can help our dev team to investigate the issue. 

Thank you for your feedback.