I'm acessing to MS Access Database. Currently I have a table called "period". The fields in this table are :
1) YearNum Integer
2) PeriodNum Integer
3) StartDate Date
4) EndDate Date

The records in the table can not have a StartDate and EndDate overlap with the other records. Eg,If the table already have a record below :
YearNum=1999, PeriodNum=1, StartDate=01-Jan-1999, EndDate=31-Jan-1999

If we try to insert a new record below :
YearNum=1999, PeriodNum=2, StartDate=15-Jan-1999, EndDate=15-Feb-1999

The program must give an error.

What is the easiest way to control it? Can we use the validation rule to control this and how?

Thank you very much in advance.