% Standard Difference

I'm attempting to create a CF for bracketing standard Bias during HPLC runs, the calculation (as outlined in our SOP's) is as follows:                         
% Bias =[ A-B /A ] x 100
Where:                       
 A: Mean area response of Standard prior to the samples (Mean of S0101)
 B: Mean area response of Bracketing standard after the samples (S0102) and  following for S0103,S0104,S0104,S0105...
 Individual 

%Bias For BKT Standard -1 :

Mean of Standard Solution (S0101) - Mean Of Standard Solution _1_BKT_1 (S0102) / Mean of Standard Solution (S0101)  *100

Is this field possible to create ?