Conditional formatting in excel using c#

 Hi,
    I am new to excel object in c#.I need to change font colour of particular text using conditional formatting.
Example
      a1-1
     a2-2
    . . . . . . . . .
    a10-10
    In my example a1 cell contains 1 till a10 contains 10.I need to change the font colour of the cell those whose cells having value as 5.
   Give me a code snippet.Thanks in advance.
...