Before you spend $$ on calibration, find out what your calibration lab offers. Many will put in a "standard" voltage (probably one for each range) and if the reading is within the scope spec they log the actual reading vs the spec and not make adjustments. Or if it is within but near the edge they will likely tweak the calibration.
Also consider you are likely using a 10:1 probe. How good is your probe?
You are best off taking Yoga to deal with your frustration 