How to enlarge textbox control when it is moused-over?

Hi All,

Io enlarge textcontrol when it is moused-over, I'm using the below:

function enlarge(textbox1)
{
  textbox1.style.height=textbox1.scrollheight+"px";
}

The problems are:-
------------------
1. How to regain the controls original height?

2. The function should be control-independent. I should be able to use this function for some other textboxes also.

3. When the control is moused-over, all other controls should be overlapped by my text control. i.e, it should hide other controls...

How to do the above using javascript...