Need VBA code for attached procedure, it looks difficult in fist sight but if you understand it is so easy as calculation is lengthy but process is simple.
In attached workbook
Sheet - TEXT is gives you general idea what is the procedure.
Sheet - LT (Member) data sheet.
Sheet - LT.Z (Sample) is process sheet as well as result sheet.
Sheet - LT.Z is calculation sheet where you can see what are the steps & its calculation.