This cheat is similar to the setav command, but instead of setting the player variable to specified value, it will add the value to the existing value.
player.modav [character variable id] [value]
|Character Variable ID||The ID of the character variable you wish to change the value of.|
|Value||The value you wish to add to the specified character variable. Use a negative number to remove value.|
player.modav charisma 5
The above command would add 5 charisma to your character.
player.modav charisma -5
The above command would remove 5 charisma from your character (as we specified negative 5).