Forms :: Make A Field As Mandatory At Current Record Level

I have one requirement i.e i want to make a particular item as mandatory for the current record in the tabular form.

so i have written code as below:

DECLARE
lv_item item;
BEGIN
lv_item := FIND_ITEM ('XXMZ_DETAIL.QTY_ACT');
SET_ITEM_INSTANCE_PROPERTY (lv_item,
current_record,
required,
property_true);
END;

This code is not effecting qty field. If i write set_item_property built-in that item becomes mandatory.But it's not effecting at current record level.It's effecting block level.

So how can i make a field as mandatory at current record level?