Given your revised working days (Sat - Wed) covers the same number of days as NETWORKDAYS default (Mon - Fri) you can simply adjust/offset the dates in the NETWORKDAYS calculation so as to account for move from Mon-Fri to Sat-Wed

Adapting daddylonglegs' formula from above:

=(NETWORKDAYS(A2+2,B2+2)-1)*(J$3-J$2)+IF(NETWORKDAYS(B2+2,B2+2),MEDIAN(MOD(B2,1),J$3, J$2),J$3)-MEDIAN(NETWORKDAYS(A2+2,A2+2)*MOD(A2,1),J$3,J$2)