Goal difference for last 3 matches wanted

[tom hatten]

Hello.
I'm trying to find the goal difference for each team over a period of 3 weeks. With the fixtures showing at the top, I want the goal difference for the home and away teams to show in columns C and D respectively. For example, over the past 3 games Cardiff have scored 5 goals and conceded 7, goal difference -2. Brighton have scored 3 and conceded 3, goal difference 0.

Thank you.