Soft Error Identifiaction

Hi All 

How to identify or capture the Soft error/warning message in Web application using Loadrunner ?

In Hard Error a pop up message is displayed, till we click "OK" or "Cancel" it will not allow execution in VUGen to execute. In Soft error it will be like a pop up message display for certian interval of time and disappears. 

While execution if LR encounter Hard error execution fails/ stops,  but in soft error LR dose not detect the message/ popup but execution completes and give success message. 

Any one know the idea how to detect the soft error and steps to handel the soft error please let me know. 

Thanks in Advance.

Thanks

Asif