Enhancement of f-54 for clearing vendor

[shivangi_pant]

Hi Folks, I have one issue. There is a tcode f-54.When we enter details on the screen of f-54, a second screen opens for clearing documents.Now i need to stop the second screen from appearing instead i want to dispay error msg. I have the exits with me but none of them is working. Can you please help me to solve this issue. Thanks in advance.
Exits are-
EXIT_SAPLBOS20_010 User-Exit before selecting the downpayments to be allocated

EXIT_SAPLBOS20_020 User-Exit after selecting the downpayments to be allocated

EXIT_SAPLE31B_100 User Exit: Determine Amount of Down Payment Request

[raymond_giuseppi]

If you want to prevent second dynpro (implicitly displayed cause defined as next dynpro) to be displayed, you should analyze the dynpro 014 logic to find some implicit enhancement options in the standard check forms that raise usual errors (period, date, vendor, etc.).

Else provide more information, what are the exact rules to apply in your check, which fields are required, etc.

[shivangi_pant]

I dont have to goto second screen at all... All the data when filled in the first screen and saved to the database then the program should give error if user try to execute second screen.
I am not sure how to use dynpro as i am new to enhancement.