Error message to be displayed in status bar and user shoud not save values!

Hi all,

I am implemeting BADi LE_SHP_TAB_CUST_ITEM for some custom fields in tcode VL31N.Now in the screen program,now for 1field.I need to check the value for the field and display an error mesage in the status bar and should not allow the values to be saved until user enters the correct value in that field.

Now my queries:

1.Im unable to display error mesage in status bar.if i display success message and use display like 'E' it display the error message ,it dislays message in status bar in red color jst like error message but the user is able to save the screen values!I dont want the usre to be able to save values when this message is displayed.

Please help.