Right now there is no UI support for adding rows in nested levels. You would have provide an external button and then add the row manually in the external data source.
With the 2.0 version (currently scheduled for release toward the end of February) we will have improved hierarchy support where each nested table can have its own Append row just like a stand-alone table.
While formula cells can be used in a hierarchical grid, there is currently no special support features added to the hierarchical structure to manage them. So you would have to determine exactly how you want your formulas to behave as you add/delete rows, and code the functionality yourself. This would likely mean that you would have to use them as unbound columns added in the virtual manner shown with the CustomersVirt sample. Currently, this is doable, but depending upon what functionality you want, it can become complex very quickly.
Here is a new QueryCellInfo handler for the Customers.cs file in that CustomersVirt sample that puts a formula in one of teh unbound columns that uses the values from the previous column in the formula.
public void QueryCellInfo(QueryColumnStyleEventArgs e)
{
GridQueryCellInfoEventArgs ce = e.GridInfo;
if (e.MappingName == "Unbound1")
{
//make value some number
ce.Style.CellValue = e.State.Position;
if (e.Level.LevelIndex == 0)
ce.Style.BackColor = Color.Cyan;
else
ce.Style.BackColor = Color.Yellow;
}
else if (e.MappingName == "Unbound2")
{
//make it some formula...
//cell is somethlike: E12
//using ColIndex to pick up the value from UnBound1 (could probably do this in a more robust way
string cell = GridRangeInfo.GetAlphaLabel(ce.ColIndex-1) + GridRangeInfo.GetNumericLabel(ce.RowIndex);
ce.Style.CellType = "FormulaCell";
ce.Style.CellValue = string.Format("=1.2 * {0} + {0}", cell);
}
}