Hi Arthur,
Could you tell us more about your application? Are you measuring settling time or something like that?
That's a precision of about 1 in 400, or close to 12 ENOB.
Even with High Res and averaging, it will be difficult to reach 12 ENOB on a scope, not to mention the fact that probes are usually not rated to more than 1% accuracy.
If your bandwidth is low enough, you should consider using a DMM, that would be the best option.
There's also the classic Jim Williams app note 74 on measuring settling time using a sampling bridge switch:
https://www.analog.com/media/en/technical-documentation/application-notes/an74f.pdf
