Changing a sector tag mid-level?

I'm using Zdoom in Hexen format, is it possible to change a sectors tag via scripting? Neither Zdoomwiki or DW search provided me with answers.

No. Why do you want to change the sector's tag? Can't you achieve the desired effect in another way?

Yes, but I'd have to calculate a ton of values for a ton of floor heights. I'm trying to have a section in my map where by hitting a switch the player has to drain an area from nukage, thus making the area accessable.

I could have the fake floors lowered to the same level as the real floor and change the fake floor tiles, but this would be a long and tidious process.