Hello.

You should be able to do it on code-behind of your bizform web part. Please see: http://devnet.kentico.com/docs/devguide/modifying_the_code_of_standard_web_parts.htm. Here you can see an example for OnAfterSave() method, which you can use for your purpose. You will need to check value of appropriate field:

viewBiz.BasicForm.FieldControls["[fieldName]"];

And according to this value redirect user to selected page using Response.Redirect() method or settings FormRedirectToUrl property for your bizform.

Best Regards,
Radek Macalik