Coverage Amount Reduced Due to Age Change to 70 Years

We are configuring Voluntary Life insurance where the coverage amount is user-entered during enrollment.

Our requirement is that when an employee reaches age 70 or older, the elected coverage should automatically be reduced by 50%.

We have observed that this reduction works correctly when the coverage is calculated using a compensation factor or is a flat amount. However, when the coverage amount is user-entered, the reduction is not applied, even after configuring the variable coverage reduction rule.

Is there a supported approach to achieve an automatic 50% reduction for user-entered coverage amounts or similar? If so, could you please advise on the recommended configuration or any alternative solution?