webforms of c#.net

Question

 hi ,

I want to create a webforms application on timesheet,here i need code for the below one

I took 3 textboxes in that 1st  textbox for entering starttime and second  textbox for entering ending time.Third  textbox for displaying click.

here ihave  one button.wen I click it the result should be display in textbox3.

pls send the code