• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
If you mean the value for provinces in peace talks, then not directly. There's no modifier that affects it (though one has been added to EU3 via HTTT's casus belli system, so it's possible we might see one in the future), however I've done some tests and the only things that affects a province's peace value are population and civilisation. As odd as it sounds, culture, religion and even cores have absolutely no effect.

Total Conquest uses an event that fires when the loser controls no provinces that reduces their civ values to between 0-9, which makes the province cost a fraction of its overall warscore requirement. After the war, the province's value jumps back up to normal.

If you're talking about modding how warscore is calculated (ie how effective battles, provinces, etc are in gaining warscore), then no, it's hardcoded.