In Your Wildest Dreams(1991)

Overview:

High school senior Mark's wildest dreams come true when he makes a simulated stock purchase that accidentally turns him into a millionaire overnight. But when he discovers that the money belongs to his girlfriend's dad, who needs the funds to save his electronics company, will Mark admit to the snafu? Or will he keep the money and pursue his dreams of wealth, even if it destroys those he cares about?