Timer控件的文本框和焦点问题（asp.net）

I am needing to create something like a lock timer(a little thing that just updates a lock time in a database). I thought the Timer control would suite my needs, but whenever the Timer control causes a partial post back, recently typed text in a textbox can disappear(inbetween the post back begin and post back end) and it loses focus.I am needing to create something like a lock ti