getting value from hidden field in update panel

i have 2 text controls one visible & other hidden & a button1 wuth client click   in update panel

when the user enters the value in visible text control & clicks button1 the value is passed to the hidden field & i get value in the hidden field

outside the update panel there is one more command button with server side click event

on command button click i need to get values of the hidden field in server side which currently i am getting blank

i even tried by putting the command button in another update panel

but stil i get balnk