These formulas belong to the Graph Package rather than to an individual graph item. They have no dedicated Argument_ variables, and their Result is not used.
OnBeforeDraw runs after the previous graph data has been cleared and before records are calculated and drawn. Use it for actions that must happen before building the new graph.
OnAfterDraw runs after record calculation, series processing and Bottom-axis range setup. Use it for actions that require the completed graph data.
Formula errors are shown to the user. Both events run during desktop drawing and the server-side graph refresh used by the web client.