Userexit USEREXIT_SAVE_DOCUMENT_PREPARE Example to change the data

Hi,

I use the EXIT MV45AFZZ Form USEREXIT_SAVE_DOCUMENT_PREPARE to check some inputted data. If the inputted data are wrong, e.g. Salesoffice, the User need a possibility to change the data again. I send a POPUP to inform the user that the salesoffice not equal the sales office in the customer master data.

How is it possible that the User can change e.g. the salesoffice?

Kind regards

Michael