Front loaded accrual plan - based on service in plan year

Summary

Need to create formula to front load accrual based on service anniversary within the plan year

Content

Hi All,

Hoping someone can help me determine the best way to go about creating a new vacation plan.  It will be a front loaded plan with the accrual based on the length of service - but I need it to look forward and determine the length of service that will be reached in that year, and provide the appropriate accrual. 

I have plans set up currently that use the regular accrual matrix and derived length of service as of the date of accrual to provide the time, but I am stumped on how to get it to pull service for plan year it is providing time for.  I am hoping a formula of some sort will do this, but I am not well versed in creating fast formulas.