I’m thinking of a data structure where you have a set number of pieces to be divided.
Let’s say the amount is 100, you want to divide it by 10, then each piece is 10.
Then use something like PayHere to pass an additional parameter to know where the payment is coming from (let’s say what rowID), then bring the payment info back to your sheet using an Integromat webhook scenario.
Then you can use a rollup on top of a rowID relation from the original sheet that contains the amount, to the sheet that contains the payments. The rollup will tell you how much money has that bill been paid.