How can I redirect if exists?

[halfa]

Newbie question....I have a data entry form, but I want to check to see if the data has already been entered...(yep, that's easy). But I want to redirect to another page if it already exists. Basically to tell the user that the data has already been entered.

I can see where I can display an error message if the record exists, but how would I go about redirecting to another page?

Cheers

 

[railer]

I need this answer, too. Thanks