[kh99]

You could create a phrase of type "Error Messages", maybe use a Varname like nopwchange and this text:

You can't change your password here. Do it <a href="{1}">here</a> instead!

Then create a new plugin using hook profile_start with this code:

if ($_REQUEST['do'] == 'editpassword' OR $_REQUEST['do'] == 'updatepassword')
{
    eval(standard_error(fetch_error('nopwchange', 'www.someurl.com/changepassword')));
}

Of course you'd change the url to the one where they can change their password. Or if you want you can take that part out of the phrase and just tell them they can't do it.