sorting

Question

Hi,

i have one grid with the 4 fields as given below

[EC No.]    [Firm Name]      [Due Amt.]     [Due Days.]

i want to allow sorting in each column in descending order...n want default sorting from Due Days fields....

suppose i want to sort grid from [Firm Name] field so it should sort data by that field

and suppose i want to sort grid by [Due Amt.] field so it should sort data by that field..vice versa

plz provide me code with example

thank you..