dynamic combo box

My webpage allows the user to select an option from a combo box. The options of this combo box are All, Name, Position and Year. How do I make another combo box visible once the user has selected either the Name, Position or Year option from the first combo box? (note: When the user clicks on the All option, I do not have to display another combo box.)

Any help will greatly be appreciated!

Use this:

<select name=first onchange="if (this.value!='all') second.style.display='block'; else second.style.display='none'">
<option value=all>All
<option value=pos>Position
<option value=year>Year
<option value=name>Name
</select>
<select name=second style="display:'none'">
<option value=all>1
<option value=pos>2
<option value=year>3
<option value=name>4
</select>

- Jemima