need to put check at the year selection

hi,

how to put this check at selection screen.

1. Program will check at the year selection, that should not be more than 3 years, otherwise, the program will raise the error message of u2018Only allow 3 years difference!u2019.

2. is there any fn module which gives the begin and end dates for a year.

requirement: determine the begin date and the end date of selection period for year selection at the selection screen.

Need this urgently.

Thanks.