=IF(AND(ISNUMBER(R2),ISNUMBER(S2)),IF(ISNUMBER(AC2),(R2-S2)/7.45,(R2-S2)/7.45+0.4),"") in Cell T2
=IF(AND(ISNUMBER(R2),ISNUMBER(S2)),100*(R2-S2)/R2,"") in Cell U2
These Cells are copied down the Worksheet
Only get values if using hydrometer ie inputs in Cols R and S
Cheers
Ian