Getting all possible combinations of records and pasting it

[01's]

Hello everyone,

need one small help.

I have a base date for forecasted sales at customer-product id-month-location level with lot many other fields.
For some combinations of product id-customer-location; there are no records since there is no forecast available.

I want to create all such records automatically with blank forecast values and add them below already existing data.
How can I do that?

Any kind of help is appreciated. Thanks very much!