autonumber (from high to low) and restart after reaching certain number

doing a project that changes what floor of a building i am on daily. due to weather delays, the original schedule is no longer accurate. I am attempting to put together an interactive schedule that keeps track of which floor i am on and what day.

I put together a formula [=IF(B2=3,39,IF(ISTEXT(C3),"",MIN($B$2:B2)-1))] that automatically counts down from 39 (the number of floors) as long as no text is in the adjacent cell (see imageSchedule of work ex.jpg). I would like it to repeat this autonumbering system after it reaches the 3rd floor. i've gotten it to go back to 39 after 3 comes up, but it still subtracts from the original 39, which i assume is caused by the MIN function I used, but I do not know an alternate function to use.

any adjustments to my formula or new simpler ones are much appreciated

Hi!

And option could be:
[B3] : =IF(ISTEXT(C3),"",MOD(LOOKUP(9E307,B$2:B2)-4,37)+3)

Blessings!

This worked perfectly. Thanks!