Updating Numerical Data In A Table, Add Not Replace

I am doing a project for my HND for a football league and i am at the point where so far everything is goin good but i need to update the League table. For those that dont know how a league table works here it is:

For a Win you get 3 points
A loss u get 0
a Draw u get 1

Any goals u score go into you 'Goals for'
And any scored against you go in your 'Goals against".

Basically i already have some ASP files where the administrator of the system types in the results for games played now i need to update this league table depending on the results. I want to execute something like this:

If HomeScore is greater than AwayScore Then Add 1 to the played field, add 1 to the Wins field, add 3 to the Points field and for the goals for and against i thought it may look something like this:

For = for + "HomeScore'
Against = Against + "AwayScore"

I have absolutely no idea how to do this, i dont know whether to use an Insert statement or an update Statement.