Hi,
First you need to write your pcr to establish the service length, you need to query the it0041 subtype to do this. Within your schema, this rule will need to be processed each day OR as at the first of April each year.
Then you need to calculate the additional leave required and add it to the time type which is the base entitlement to your quota (t559L is the quota overview linking all of the t559 tables which your quota needs to refer to). Alternatively, you can update your quota with the additional leave using the update quota operation.
Are you ok with the theory and the broad overview or do you need to know how to query IT0041 in your pcr and how to update quota or add to base entitlement?
Let me know, I hope this helps.
Will