How to give different message text for standard raised exception?

Hello Experts,

I have requirement that i need to show one error message in web-dynpro screen as pop-up. In background standard is handling the error. for display the error one exception is getting raised and based on Web-dynpro screen it is displaying.

I want to show the error but with different message text. How can I able to change the text of the raised Exception?

Thanks

Pravasini