Dear Prasoon,
Please find the below screenshot. in ME21N transaction we are having different document type maintained.in additional data tab we are maintaining validity start date and validity end date.
in this system is allowing us to enter the validity end date more than year. we need to control this with in 90 days.system has to check the difference between validity start and end date. if difference is more than 90 days system has to through error message validity period is more than 90 days.
Ganesh