drop down list in code behind

Hello,

I would like to populate my dropdown list in the code behind with numbers.

but i need it to count down in 0.5

so if a user has 7 days holiday i want to have the drop down menu go

7/6.5/6/5.5/5/4.5/4/3.5/3/2.5/2/1.5/1/0.5

and if the have 3 it would be 3/2.5/2/1.5/1/0.5