How to call server side function at cliet side

Question

Hi friends,
I am working on one appliction, In that on leaving one textbox i want to fill values in other textboxes and that value will come from database.
Since there is no server side event for lost focus for text box. I am going to call javacript function at "onblur" event of that text box and in that javascript function i want to call server side function(so that i can get values from database).
And friends i want to do this without using AJAX.
So if anybody have any idea then pls let me know.

Thanks in advance.

Mehul