>hi,
>
>thank you for reply,
>
>i create program aaa
>
>i put your code inside, i run this program ,i get nothing.
>
>how i can let this code work at my form.
>
>thanks for help and time.
>
>best regard.

Mohammed,

Create a class based on a text box. Place the code I provided for the Valid event there. Create a form and from the Form menu add a method. Add the code to calulate the difference there. In the LostFocus event of the second (or end time) text box, place the code to call the method.

Beyond this, I can't be of further help.