LPpan 24 hours per year, prorated for new hirs

Looking to see if anyone has a plan set up to accommodate giving employees 24 hours on Jan1 but then employees hired between Jan through June will get 24 hours immediately, employees hired July through December will get 12 hours.  No carryover.  I've never created a plan exactly like this before and want to automate it.

Any help is appreciated.

Full policy is:

• Full time employees shall receive a bank of 24 hours of FLEX time per calendar year; prorated for part time FTE status, after the completion of 90 days of employment.
• New full-time employees that begin employment January through June shall receive 24 hours FLEX time for the calendar year; prorated for part time FTE status.
• New full-time employees that begin employment July through December shall receive 12 hours FLEX time for the calendar year; prorated for part time FTE status.

• FLEX hours are loaded on 1/1 and is available for immediate use.
• FLEX may be taken in the shortest increments as permitted by the payroll system (15 minutes)
• FLEX time is not eligible to carry/roll over to the next calendar year.

Status Changes

• Full time employees who change their status to part time mid-year shall not have a reduction to their FLEX time balance; FLEX hours will appropriately adjust to the part time hour allotment on 1/1 of the following calendar year.
• Part time employees who change their status to full time mid-year shall receive a deposit of 12 FLEX hours effective with the date of the status change.