Generation of employee id

Question

I have form empdetails like this

EmpId:textbox Name:textbox
username:textbox Password:textbox

I need to generate empid and it start with 0001 and display it in the empid field and all other information will be entered employee and i have provided save button when the user clicks on it it should be saved in the db and next time when the user clicks on this form it should display empid as 0002 and the process continues.When the user clicks on the save button it should be saved in the db and it should display in the gridview with id and name field made it as hyperlink it should look like this.

ID               Name

0001            Sweety

Can any1 help me on this

With Regards,

Sweety