Validation based on variable date

Hi all,

I need help in validating customers based on dates...the DSO has contract start date and end date....based on which i need to figure out two things..

1) based on a user input date(variable date) if the contract is active or inactive

- active customers if variable date is in between start and end date.

- inactive customers if variable date is greater than end date

2) Be able to select specify active or inactive or both in the selection screen. Currently there is no field on the DSO that determines active or inactive customer.

So ineffect if the user select todays date and then select active....the result set should include only active customers based on todays date.

Thanks