In that case, yes it is. You change one and the other has to be done all over again. What you are looking for is a split printing technique where you lay down the highlight, then shadow. Our own Ralph has a chapter in his book "Way Beyond Monochrome II".
I do not use this method in my own darkroom.
Doing it the old fashion way, you do get a feel for it though. You will be able to say, "if it look like this #2 at 10 seconds, let's try #2.5 at 9 seconds and see...." and get it pretty much right.