Lot Size Procedure (lot for lot and periodic)

Hello Experts,

In PPDS planning , i have a requirement to club order quantities less than 20 MT upto 20 and any order quantity more than 20 to be lot for lot for the same product. I.e if demand is for  4, 5, 5 and 6 MT, the planned orders should club to 20 MT at the same time if another demand appears at 55 MT then Planned orders of 55 MT should flow. Is there a way to achieve both the above in standard material master setings ?

Regards

Alin