queston about application form, how can prevent applicant to re apply?

I have an application for where I do save applicant userid and username once he submits the application. and its stored in db
just wondering how can I prevent the applicant who applied to re apply again and show hi a message that he already applied?

its ok ive fixed it, but I need to know how do I do logic control over the file up;load action, if the uploaded type is not accepted or the size exceed the allowed send back to the upload.

Hi saveg,
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Having an Event Loader in the On Fail box set to the 'load' event' of your form should do what you need.
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Bob