Mark listbox as mandatory

Hi,

I have a custom screen with a listbox created in it.

In the POV event I'm using FM  F4IF_INT_TABLE_VALUE_REQUEST to populate the listbox with data.

My requirement is to make the listbox mandatory, so I marked it as required in the screen painter. But then the listbox stays empty !

I tried then to control if the field is empty or not in the PAI event:

FIELD ... MODULE ...

and I used a message of type 'E' if the listbox is not filled by the user, but I faced the same problem again: the values are not fetched.

Thanks in advance.