The SetUnderlying command sets the value of the underlying for node j at level i of the tree T. See Finance[GetDescendants] for more details about node indexing.

with(Finance):

T := TrinomialTree(5, <1, 2, 3, 4, 5, 6, 7>);

$T:=\mathbf{module}\left(\right)\mathbf{end\; module}$

TreePlot(T, thickness = 3, gridlines = true);

GetUnderlying(T, 4, 1);

$1.$

SetUnderlying(T, 4, 1, 2);

GetUnderlying(T, 4, 1);

$2.$

SetUnderlying(T, 4, 1, 2);

SetUnderlying(T, 4, 7, 6);

TreePlot(T, thickness = 3, gridlines = true);

The Finance[SetUnderlying] command was introduced in Maple 15.

For more information on Maple 15 changes, see Updates in Maple 15.