Prevent Duplicate Entries in the table

[vinamr]

Hi,

I have an online application form that a member submits to register with our organization. However I want to make sure that the member submits only one application form per session year. Is there anyway I could prevent the member from re-submitting their application. The current setup lets them submit many applications which I am trying to prevent.

I was advised to use a server side custom validation to prevent duplicate entry. The validation can be performed on Parent_ID which should be unique in the registration table. If the parent_ID exists the form should pop-up an error message. Can someone please provide me some sort of a function to accomplish the above?

Any help is greatly appreciated.

Thanks
VinnyVinny