Fill scripts are typically used to read records from tables other than the table linked to the scrolling window. Because this increases the time required to fill the scrolling window, avoid using fill scripts for scrolling windows whenever possible. Instead, consider adding the fields being read by the fill script to the table linked to the scrolling window.
Also, try to avoid using the reject record statement in the scrolling window fill script because many additional records may have to be read and rejected before the scrolling window is filled. If several records shouldn’t be displayed in a scrolling window, either set a range on the linked table or consider using a temporary table.