bbbutton help

i have made my bbbutton code

<div style='padding-left: 5px; padding-top:5px;'>
<input type='button' value='B' name='btnBold' onclick='wrapText(document.getElementById('inputforum'),'<b>','</b>');'>
<input type='button' value='I' name='btnItalic' onclick='wrapText(document.getElementById('inputforum'),'<i>','</i>');'>
<input type='button' value='U' name='btnUnderline' onclick='wrapText(document.getElementById('inputforum'),'<u>','</u>');'>
<input type='button' value='IMG' name='btnImg' onclick='wrapText(document.getElementById('inputforum'),'<img src="','" />');''>
<input type='button' value='URL' name='btnUrl' onclick='wrapText(document.getElementById('inputforum'),'','');'>
<input type='button' value='PHP' name='btnPHP' onclick='wrapText(document.getElementById('inputforum'),'[php]','');'></div>
but i have no idea how to make it so like on here when you hit the link button a box comes up so you can enter the url?? this is the same with the images... can any 1 shine any light ointo this?
also is there any other features i could add to this?

It's calling a window.prompt() function like
window.prompt("Enter the url");

hey thnaks iv looked into them via google but i have no idea ow to use it within my bbcode via <input type='button' value='URL' name='btnUrl' onclick='wrapText(document.getElementById('inputforum'),'','');'>