That's true. However, I didn't want to prevent going above the HP max because temporary hit points might allow someone to legitimately do so. And while in 5e it's not possible to go below 0 HP, it is useful to see how much below 0 HP an attack *would* put someone, because of the rule about instant death due to massive damage. The other issue is that in normal situations (no temp HP or instant death), corrections need to be made at the time the HP value goes outside the allowable range. For example, someone with an HP max of 20 takes 10 damage, then receives 15 healing, then takes 8 damage. If your formula is just adding up the numbers, it will tell you they have 17 HP remaining. But they should have 12 HP, because only 10 out of the 15 healing they received should have counted. An ifs statement would see 17 as a valid result, and not be smart enough to know it should have made a correction partway through adding things up. It is possible to create a formula that accounts for this, but that would make the spreadsheet MUCH more complicated, and put it beyond the skill level of anyone but advanced Excel users. That's why I decided it was better to manually make the corrections. Hope you find this helpful.