How to limit deviation between samples

Dear colleagues,

I currently have the challenge that our QM analysts want to record a characteristic with 2 sample values and mean value in tolerance range.

Up to here this is standard. Additionally he wants to check the limit the mean absolute deviation to a certain value.

E.g.:

mean absolute deviation is 0,5

mean value between 1,8 and 2,2

sample 1: 1,5 ppm

sample 2: 2,5 ppm

mean absolute deviation: 1 (==> NOK)

mean value = 2 (==OK)

===> characteristic is out of range even if mean value is in target value range.

Currently I covered this with having two separate characteristic for the samples 1 and 2 and additionally 2 calculated characteristics, one for mean absolute deviation ( ABS(S1-S2) < 0,5) and one for mean value ( 1,8 <= (S1+S2)/2 <= 2,2).

Nevertheless this should be possible with only one characteristic and customized sampling procedure.