How to Set Default value for datagridview combobox column

Question

How to Set Default value for datagridviewcombobox column when it creates new one..

I have situation user enter the shift basis calculation

and it use datagridview

 

when form load and new row creates default value can load .if user need modified value then user change otherwise it remain same...

how can code this..

 

i'm also tried datagridview_cellformatting event()..

it changes when user enter and after new row creates changed to default values  

help me folkz