Stacked Benefits-Critical Illness Insurance

I have been asked to setup a Critical Illness plan in PeopleSoft that consists of 3 plans:

1. Employee: 10K, 20K, 30k
2. Spouse: 5K, 10K, 15K
3. Child 5k, 10k, 15k

Both the EE and SP plan are age based rates with the Child being flat rate based on the purchased amount. Both the EE and SP plans are what the vendor is calling a stacked benefit.

Example: John Doe is 20 years old and buy 10K of coverage. At age 35 he buys an extra 10K of coverage with a total of 20K. The premium for John Doe should be 10K at the age rate when he was 20 and 10K at the age rate when he was 35.