To implement this you want a function which can be called when the player on the webpage submits a modification to the tax level?
OR
You want a function to be called by when the DM hits a button to process turns. Where this function will be called & cycle through every province in the Province table.
I reference TaxLevel (in Province table) to find the if the taxes are light (add one to loyalty), severe (minus one from loyalty) or other (no action required). Creating a temporary table which lists the ProvinceID as it’s key.
The disadvantage I see is you then need a commit function to put this all back in to the province’s Loyalty or LoyaltyModifier after the other DM see’s it.
I tough about an adjustment that that will be made for all provinces after the 3 round which is control by the dm (so like the option 2) since the adjustment are made only at the end of a domain turn.