When this tool is already activated, the first mouse-move will call CopyPrototype and add the resulting object, as the NewObject, to the view. Further mouse-moves will continuously resize the NewObject (or the NewObject's SelectionObject if ResizesSelectionObject is true) according to the bounds returned by ComputeBox.

If this tool is started but not yet activated, mouse-moves are ignored when Modal is true until a mouse-down activates this tool. When Modal is false, a mouse-move automatically activates this tool so that the NewObject is created and mouse moves resize it.

Reference

GoToolCreating Class
GoToolCreating Members