Like so
<html>
<body>
<form onSubmit="
window.document.all.blah.href='#';return false;">
<input type="submit" onClick="
window.document.all.blah.href='#';alert('its disabled');">
</form>
<a href="blah.html" id="blah">the link</a>
</body>
</html>
That will disable the link(not visually) by clicking the button or submitting the
form(pressing enter). If you want it to look disabled too, go like this:
<html>
<body>
<form onSubmit="
window.document.all.blah.href='#';return false;">
<input type="submit" onClick="
window.document.all.blah.href='#';alert('its disabled');
window.document.all.blah.style.color='#c5c5c5';">
</form>
<a href="blah.html" id="blah">the link</a>
</body>
</html>
Hope that helps