I have posted here a few times asking for some guidance, but this time, I think I might add value.
I enjoy some of the Sudoku variants, like Killer Sudoku, but was getting really tired of trying to figure out which combinations of digits summed to the appropriate value. So, purely out of laziness, I developed an Excel spreadsheet with macros, available here: http://pairofdocs.net/wp-content/uploads/2023/05/KillerCheck.xlsm, that allows entering the digits (in up to six cells), the value to which these digits sum, and will show you which are the legitimate digits. It is assumed that digits cannot repeat, but in some case they can, so simply put any character in ‘Allow Dupes’ box.
Hope that someone finds this helpful.