How to insert a blank row between two rows of list names in data validation

I try to have an empty row to seperate the two series of names.
In data validation list, I enter 1,2,3, ,a,b,c but it does not
create an empty row. I could add a dot liked this 1,2,3,.,a,b,c
but I prefer an empty row

Below is the result I like to get.

1
2
3

a
b
c

Thanks

You would create your list in a reference range of cells with the blank cell in the middle, then use that range of cells as the source for your Data Validation:

http://screencast.com/t/F5nRUx7u