Continue bullet numbers from one slide to another

I frequently use Keynote to organize lecture material. One problem is that often material on a given topic takes multiple slides. I like to use tiered numbers to organize material. But those numbers do not continue between slides, so if one slide ends at 4.2.2 I have to do a lot of manual tinkering to get the the correct number on the next slide, regardless of whether it is 4.3 or 4.2.3. This also means that I hate to revise a presentation because any change might mean that I have a lot of manual work on tiered numbers to do. Does anyone know a solution to this problem that I have missed? If so, I would really appreciate your help. Thanks in advance.