Leaving the screen

Hi All-

I want to come out of the main program if the condition failed in the user-exit...

I have standard SAP program(SAPMQEVA) and inside that there is a user-exit(EXIT_SAPMQEVA_010 ). Whenver the cursor goes inside the user-exit and if the condition failed then the entire process should terminate and come out of the main program and the screen we get after logging into the SAP system(when we first enter the transaction) should appear.

Plz help me.

Sharadendu