If you can make it 110K instead of 100K for the lower part of the tap then that will make it more accurate 100:1 as the 110K in parallel with the 1M of the scope will be very close to the 100K.
Note also that capacitance around the 9.9M will effect frequency response. The compensation adjustments in the scope adjust for that for normal probes but may not be right for a self-made one. That may not be a concern if you are only interested in relatively low frequencies.