Update Cost Rates with an Existing End Date

I need to upload rate schedule rates where a cost rate may have a start / end date.

The use case is, we load cost rates for one year ahead so we can use same rates for actuals as budgets. we will have one row from 1/1/24 to 12/31/24.

Mid year soemtimes we get rate changes and need to then:

change the 1/1/24 to 12/31/24 row to end date on lets say 6/30/24

enter a new row 7/1/24 through 12/31/24

We can not leave the to date blank as we will also have 2025 rates already.

How am I able to update the existing row with a new end date to load in a new row with the day after that end date?