R5-New to Designer....Calendar Question

I am new to Domino Lotus Script and creating Databases in Lotus Domino R5. I would like an example (I am not sure if you would use LotusScript or what) of how to do the following:

On a Form there is a Calandar field. This Field is a representation of when something will expire. I would like to recieve an e-mail when the set date in the calandar field is the is equal to the real date.

Could some one help me out with a few examples or lead me in the right direction???

Thanks
BH2