System capability to calculate entitlements across multiple leave profiles

So for example, if someone changes leave profile part way through the year, it would be good if the system could calculate how much leave someone had in their existing profile up to the date of change, as well as calculating the revised profile from the date of change. At the moment, the system only makes the latter calculation, so you have to go back into the profile and add the additional leave back into the profile

e.g. If someone was full time from 1st Oct - 31 Dec and then went to 3 days per week, by setting an end date of one profile and start date of the other, it would recalculate what their entitlement should be based on working 3 months full time and 9 months at 60%