Valuettransfer on tabevent from one textbox to another texbox

See more:

C#2.0

C#

Hiin my .aspx page, I have four textbox, textbx1,textbox2,textbox3 and textbox4.I want do a calculation that if i enter value in textbox1, its value should be focous in textbox4, same as when i enter the value textbox2,textbox3 , it shouldbe foucus in textbox4 for there sum, plz can any one helpm how can i do it.
Thanks in advance