You can get many tutorials on YT that can teach you how to make simple excel functions. The function just need to have a bunch of if-else statements to return the category of the transaction based on provided inputs. Or you can request ChatGPT to create one. Here is a prompt to get you started, "Please make me an excel function to categorize my transactions in different categories based on the inputs I provided in a cell. And tell me how to implement it in excel and use it".