How to call the transaction VL02N in the userexit.

Hi all,

I am doing code in the userexit SAVE_DOCUMENT_PREPARE of the include MV50AFZ1. I'm doing some validations there. If the validations fail, i should not allow the user to post the goods. Instead i need to make the user to go to the screen VL02N once again and do the posting once again. But i dont know how to call the same screen VL02N once again through the userexit.

Can you please suggest me in doing this.

POINTS PROMISED.

Regards,

Buvana Anguchamy