Field in Postbit

[NuclioN]

I wonder how to let members choose a 'yes or no' in their profile..and when they choose 'yes' an extra line apears under the avatar with something like this:

<tr>
<td valign="baseline" align="right" nowrap="nowrap"><span class="smallfont"><font color="#aaaaaa">
$post[username]'s:
</font></span></td>
<td valign="baseline" align="left"><span class="smallfont">
<a href="#IRC" onClick="window.open('$post[userfieldX'?session[sessionurl]','key','WIDTH=245,HEIGHT=100,scrollbars=no,left=5 0,top=50,screenX=50,screenY=50 ');return false">sound</a>
</span></td>
</tr>


This code should be specific so if they choose 'yes' the userfieldX will become a wav or au file in the postbit. Maybe the yes or no can be skipped and is another method more usable.