You could and it should work just fine but it would require rewriting the whole thing as these would be the Hit Points that drive the progress bars, not the other way round.
I wouldn’t use the above method for something like this, though - it would be overly complicated having to calculate and store each bar’s progress data. Have a look at my very first post where I briefly describe an alternative method (The second method[…]) - a much more reasonable approach in this case.
If you wanted to handle HP, Armour and Shields bars that can be gradually and independently depleted (so damaged armour can mitigate just a portion of the incoming damage, for example), consider using 3 progress bars only. The division into smaller elements should be done in the material by adjusting the UV coordinates and would be decorative only.
Feed the dynamic material Max Health divided by Health Block Value and use it as the horizontal coordinate. Use the progress bar with the Map To Range node.