HOW TO MAKE EACH TEXTBOX PERFORM SUMMATION

Question

Dear Code Masters,

 

I am developing a program within the user interface i about ten(10) rows of textbox each rows have Six(6)  textbox the last textbox is made for to sum each rows.

 

see the picture below 

can any body show me how to allow each textbox sum as you enter figures because i have tried lost focus it works but when you make any changes it wont sum again.

 

any help please