Rpg Maker Developers Group

ok heres a stumper for me. it seems rather simple but i cant figure it out for some odd reason 

im trying to make a property tax system with events in which you must deposit X amounts of gold per week. what got me stumped is calling up the remainder of how much you still need to pay or deposit to completely pay off the taxes for that week. 

Concept.: payment box etc in which you can continuously deposit money into until you have fulfilled or exceeded the amount required that week. if you only deposit a portion of the amount, when you return to deposit again into the box itll show a text of your character saying "i have X left to pay this week." once the desired amount of gold is deposited if the player should come back to the box a text saying all taxes has been paid off will appear.

heres a picture to what i have already done maybe this might help the people who dont quite understand where im getting at. i added 2 pictures because the event page was too long for just one shot. the second picture dont really matter though 

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