Open a recordset of the table
For each record where Quantity > 1
Create a loop based on (quantity - 1)
Insert into the table
** Insert into yourtable (c1,c2,c3,c4) values("Tshirt","Big","Blue",1);
Alter the original record to 1
** Update yourtable set c4 = 1 where you pk = something;
move to...