Use of Standard deviation function for more number of columns

HI,

 In SSRS, i want to use stdev() funtions with 31 columns. how to use that. for ex: Patient admitted on each day per month.

Column list:  site, patient D1 D2 D3 D4.............. D31

Values    c004 alex      1  2   1   0...................1

                   c004 bret     0   0   0   1...................3

Here i have to find the StDev value for D1 to D31 columns. How to use the Stdev() for multiple columns. 

Regards,
Fazlu.